| In millions, except per share items | Sep-30-19 | Sep-30-18 | Sep-30-17 | Sep-30-16 | Sep-30-15 | Sep-30-14 | Sep-30-13 | Sep-30-12 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net income | 2,208.0 | 1,473.0 | 872.0 | 842.0 | 813.0 | 787.0 | 675.0 | 586.0 |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation and amortization | 148.0 | 142.0 | 102.0 | 92.0 | 91.0 | 95.0 | 86.0 | 72.0 |
| Amortization of acquired intangible assets | 125.0 | 141.0 | 79.0 | 86.0 | 90.0 | 90.0 | 91.0 | 92.0 |
| Deferred income taxes | 26.0 | -24.0 | -11.0 | -8.0 | -23.0 | -27.0 | 10.0 | 5.0 |
| Gain on business-related divestiture | -60.0 | | | | | | | |
| Stock-based compensation | 47.0 | 60.0 | 36.0 | 34.0 | 36.0 | 32.0 | 29.0 | 41.0 |
| Provision for doubtful accounts on client and other receivables | 13.0 | 69.0 | 6.0 | 5.0 | | | | |
| Other, net | 25.0 | 18.0 | 12.0 | 16.0 | 7.0 | 85.0 | 75.0 | 95.0 |
| Changes in operating assets and liabilities: | | | | | | | | |
| Investments segregated and on deposit for regulatory purposes | -16.0 | 831.0 | 1,521.0 | -2,424.0 | -1,189.0 | 778.0 | -1,864.0 | |
| Receivable from clients, net | 1,985.0 | -5,536.0 | -2,079.0 | 824.0 | -1,131.0 | -2,655.0 | -337.0 | -588.0 |
| Other receivables, net | -7.0 | -129.0 | 41.0 | -16.0 | 3.0 | -10.0 | -19.0 | -3.0 |
| Securities owned, at fair value | -48.0 | 823.0 | -25.0 | -573.0 | 194.0 | 438.0 | 1.0 | 386.0 |
| Other assets | -18.0 | -39.0 | -5.0 | -17.0 | 45.0 | -39.0 | 4.0 | |
| Payable to brokers, dealers and clearing organizations | -48.0 | 823.0 | -25.0 | -573.0 | 194.0 | 438.0 | 1.0 | 386.0 |
| Accounts payable and other liabilities | 75.0 | -20.0 | 31.0 | -58.0 | 39.0 | -20.0 | -43.0 | 32.0 |
| Net cash provided by operating activities | 7,620.0 | -4,522.0 | 402.0 | 1,484.0 | 746.0 | 1,025.0 | 739.0 | 592.0 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Purchase of property and equipment | -199.0 | -229.0 | -197.0 | -105.0 | -71.0 | -144.0 | -144.0 | -186.0 |
| Cash received from business-related divestiture | 62.0 | 12.0 | | | | | | |
| Purchase of investments available-for-sale, at fair value | -1,395.0 | -393.0 | -66.0 | -1,362.0 | -506.0 | -4.0 | -4.0 | -155.0 |
| Proceeds from sale of investments available-for-sale, at fair value | 299.0 | 643.0 | | | | | 154.0 | 4.0 |
| Other, net | 20.0 | -3.0 | | | 3.0 | 2.0 | 2.0 | 2.0 |
| Net cash used in investing activities | -1,212.0 | 92.0 | 827.0 | -863.0 | -60.0 | -117.0 | 96.0 | -377.0 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Proceeds from issuance of long-term debt | | | | | | | | |
| Payment of debt issuance costs | -12.0 | -3.0 | -8.0 | | -11.0 | | | |
| Net payments on securities sold under agreements to repurchase | -96.0 | -1.0 | 97.0 | | | | | |
| Proceeds from senior revolving credit facilities | 1,800.0 | 3,225.0 | | | | | | |
| Principal payments on senior revolving credit facilities | -1,800.0 | -3,225.0 | -385.0 | | | | | |
| Payment of cash dividends | -667.0 | -477.0 | -379.0 | -362.0 | | | | |
| Purchase of treasury stock | -969.0 | -255.0 | | -352.0 | -364.0 | -190.0 | -5.0 | -208.0 |
| Purchase of treasury stock for income tax withholding on stock-based compensation | -14.0 | -17.0 | -27.0 | -30.0 | -23.0 | -17.0 | | |
| Net cash used in financing activities | -763.0 | -782.0 | 465.0 | -744.0 | -168.0 | -510.0 | -688.0 | -332.0 |
| |
| Supplemental cash flow information: | | | | | | | | |
| Interest paid | 154.0 | 118.0 | 59.0 | 54.0 | 30.0 | 30.0 | 32.0 | 34.0 |
| Income taxes paid | 683.0 | 352.0 | 483.0 | 519.0 | 498.0 | 489.0 | 379.0 | 313.0 |