| In millions, except per share items | Dec-31-22 | Sep-30-22 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 | Jun-30-21 | Mar-31-21 |
| | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q |
| Cash Flows From Operating Activities: | | | | | | | | |
| Net income (loss) | -270.2 | 277.6 | -72.4 | 285.3 | -1.3 | 66.3 | -118.0 | 240.2 |
| Adjustments to reconcile net income (loss) to net cash from operating activities: | | | | | | | | |
| Amortization of premiums and discounts on investment securities, net | 9.5 | 15.0 | 22.8 | 32.5 | 42.3 | 51.4 | 62.6 | 72.0 |
| Amortization of deferred debt issuance costs on term notes payable and convertible senior notes | 0.7 | 0.7 | 0.6 | 0.6 | 0.9 | 0.8 | 0.7 | 0.6 |
| Provision for credit losses on investment securities | -0.3 | 1.4 | 1.7 | | 3.3 | 0.2 | 6.3 | |
| Realized and unrealized losses (gains) on investment securities | 347.8 | 5.0 | 197.2 | 51.2 | -5.0 | -28.8 | 34.1 | -131.7 |
| (Gain) loss on servicing asset | -425.4 | | | | | | | |
| Realized and unrealized (gains) losses on interest rate swaps, caps and swaptions | -34.3 | | | | -27.8 | | | |
| Unrealized losses (gains) on other derivative instruments | 65.9 | 40.2 | -2.0 | -90.3 | -109.4 | 77.1 | -16.4 | 43.5 |
| Gains on mortgage loans held-for-sale | 0.0 | | | | -1.8 | | | |
| Equity based compensation | 1.7 | 2.4 | 3.5 | 4.2 | 2.5 | 2.6 | 4.6 | 1.8 |
| Purchases of mortgage loans held-for-sale | -0.3 | | | | -64.0 | | | |
| Proceeds from sales of mortgage loans held-for-sale | | | | | | | | |
| Net change in assets and liabilities: | | | | | | | | |
| (Increase) decrease in accrued interest receivable | 1.7 | -7.4 | -5.1 | 1.1 | 1.4 | 3.9 | 9.0 | 6.6 |
| Decrease (increase) in deferred income taxes, net | 9.6 | 20.9 | 25.9 | 48.8 | 2.1 | 0.3 | -21.0 | 24.5 |
| Increase (decrease) in accrued interest payable | 45.4 | 26.8 | 11.8 | -8.4 | 7.9 | -7.4 | 6.1 | -9.8 |
| Change in other operating assets and liabilities, net | -39.6 | 14.6 | 9.3 | -4.2 | -1.9 | 12.3 | -1.1 | 0.3 |
| Net cash provided by operating activities | 236.0 | 369.2 | 69.5 | -51.3 | 43.5 | 229.6 | 213.8 | -63.4 |
| |
| Cash Flows From Investing Activities: | | | | | | | | |
| Purchases of available-for-sale securities | -1,175.7 | -2,190.9 | -4,685.9 | -2,610.0 | -2,337.5 | -4.4 | -21.4 | -131.3 |
| Proceeds from sales of available-for-sale securities | 2,770.8 | 683.7 | 2,326.5 | 2,012.6 | 1,171.3 | 502.3 | 2,549.6 | 2,050.9 |
| Principal payments on available-for-sale securities | 165.7 | 249.6 | 316.0 | 371.7 | 515.0 | 647.2 | 938.1 | 1,047.4 |
| Purchases of trading securities | | | | | | | | |
| Purchases of mortgage servicing rights, net of purchase price adjustments | -30.5 | -60.9 | -50.7 | -487.8 | -109.5 | -268.1 | -196.4 | -168.2 |
| Proceeds from (payments for) sales of mortgage servicing rights | | | | | | | | |
| (Purchases) short sales of derivative instruments, net | -71.3 | | | | | | | |
| Proceeds from sales and settlement (payments for termination and settlement) of derivative instruments, net | -147.1 | 113.0 | 52.6 | 107.5 | 31.6 | -9.5 | 32.6 | -14.8 |
| Payments for reverse repurchase agreements | -1,274.1 | -832.3 | -754.1 | -381.3 | -394.4 | -300.2 | -175.5 | -304.9 |
| Proceeds from reverse repurchase agreements | 414.4 | 784.1 | 733.7 | 377.3 | 344.7 | 285.2 | 181.5 | 320.4 |
| Increase in due to counterparties, net | 155.6 | -1,141.7 | 1,388.8 | -142.6 | 252.5 | -258.6 | -49.7 | 94.6 |
| Net cash (used in) provided by investing activities | 882.2 | -2,247.8 | -674.2 | -711.5 | -474.2 | 626.4 | 3,257.7 | 2,904.1 |
| |
| Cash Flows From Financing Activities: | | | | | | | | |
| Proceeds from repurchase agreements | 6,689.4 | 11,627.1 | 9,655.7 | 7,955.4 | 4,321.9 | 5,881.7 | 7,754.8 | 11,976.0 |
| Principal payments on repurchase agreements | -8,120.4 | -9,551.3 | -9,570.1 | -7,739.2 | -3,789.1 | -7,108.6 | -11,080.2 | -15,443.9 |
| Proceeds from revolving credit facilities | | 310.0 | 260.0 | 150.0 | | 35.0 | 97.5 | 164.0 |
| Principal payments on revolving credit facilities | -12.3 | -4.6 | -5.0 | | | -147.8 | -7.4 | -4.4 |
| Proceeds from convertible senior notes | | | | | | | 0.0 | 279.9 |
| Principal payments on Federal Home Loan bank advances | | | | | | | | |
| Proceeds from issuance of common stock, net of offering costs | 0.9 | 5.4 | 0.1 | 0.3 | 193.8 | 256.6 | 0.1 | 0.1 |
| Repurchase of common stock | | | | | | | | |
| Dividends paid on preferred stock | -13.7 | -13.7 | -13.7 | -13.7 | -13.7 | -13.7 | -13.7 | -22.4 |
| Dividends paid on common stock | -59.1 | -58.8 | -58.8 | -58.7 | -53.6 | -46.8 | -46.6 | -46.5 |
| Net cash provided by (used in) financing activities | -1,566.7 | 2,313.9 | 268.1 | 150.3 | 659.2 | -1,143.6 | -3,295.7 | -3,515.2 |
| Net (decrease) increase in cash, cash equivalents and restricted cash | -962.2 | | | | -557.8 | | | |
| |
| Supplemental Disclosure of Cash Flow Information: | | | | | | | | |
| Cash paid for interest | 60.7 | 49.1 | 17.6 | 25.8 | 9.2 | 26.0 | 15.2 | 30.9 |
| Cash (received) paid for taxes, net | -1.1 | -0.5 | 0.0 | 0.0 | -1.1 | -22.3 | 0.0 | |
| Noncash Activities: | | | | | | | | |
| Dividends declared but not paid at end of period | | | | | | | | |