| In millions, except per share items | Mar-31-18 | Dec-31-17 | Sep-30-17 | Jun-30-17 | Mar-31-17 | Dec-31-16 | Sep-30-16 | Jun-30-16 |
| | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q |
| Cash and Cash Equivalents, at Carrying Value | | | | | | | | |
| Operating activities | | | | | | | | |
| Net income | 0.1 | -95.7 | 6.4 | 4.2 | 5.7 | 1.7 | 8.1 | 4.2 |
| |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation and amortization | 32.6 | 39.9 | 42.4 | 42.9 | 35.7 | 42.3 | 43.7 | 41.0 |
| Stock-based compensation | 3.7 | 3.7 | 3.8 | 4.3 | 2.7 | 4.2 | 4.3 | 4.9 |
| Amortization of premium on investments | 0.1 | 0.1 | 0.2 | 0.4 | 0.5 | 0.7 | 0.6 | 0.4 |
| Deferred income taxes | 0.6 | 13.7 | -3.5 | 2.2 | 1.9 | -8.0 | -6.2 | -0.5 |
| Unrealized foreign currency gain | -0.8 | -0.2 | -0.7 | -0.9 | -0.2 | 0.7 | 0.8 | 1.4 |
| Other | 0.1 | 1.6 | 0.1 | 0.5 | 0.1 | 1.6 | 0.7 | 0.0 |
| Changes in assets and liabilities: | | | | | | | | |
| Accounts receivable | -13.1 | -10.7 | -2.0 | -1.1 | 31.9 | -31.6 | 7.0 | 4.1 |
| Prepaid expenses and other assets | 9.5 | -14.5 | 4.7 | -5.8 | -7.7 | 21.5 | -9.9 | -5.8 |
| Accounts payable | 1.3 | -0.9 | 0.7 | -0.1 | -0.8 | 1.2 | -0.5 | 0.1 |
| Accrued and other liabilities | -4.3 | 3.2 | -0.2 | 2.6 | -5.6 | 5.4 | 2.4 | 1.4 |
| Deferred revenue | 3.3 | 3.9 | -11.6 | -21.7 | 7.0 | 27.7 | -20.4 | -16.9 |
| Net cash provided by operating activities | 33.2 | 38.2 | 40.4 | 27.7 | 71.2 | 67.5 | 30.6 | 34.1 |
| |
| Investing activities | | | | | | | | |
| Purchases of investments | -3.3 | | | | -3.9 | | | |
| Maturities of investments | 12.5 | 23.8 | 23.5 | 33.9 | 25.9 | 12.1 | 5.7 | 7.3 |
| Purchases of property and equipment | -0.7 | -0.2 | -0.3 | -0.4 | -0.4 | -0.7 | -0.9 | -1.1 |
| Acquisitions of patent assets | -17.3 | -51.9 | -12.6 | -10.5 | -27.4 | -45.7 | -34.5 | -20.5 |
| Net cash used in investing activities | -8.8 | -31.4 | 3.4 | 1.4 | -5.8 | -42.5 | -61.3 | -44.1 |
| |
| Financing activities | | | | | | | | |
| Repayment of principal on term debt | | -91.3 | -1.9 | -1.9 | -1.3 | -1.3 | -1.3 | -1.3 |
| Proceeds from exercise of stock options | 0.1 | | 0.1 | 5.5 | 0.4 | 0.1 | 3.4 | 0.2 |
| Taxes paid related to net-share settlements of restricted stock units | -1.9 | -1.2 | -1.2 | -1.6 | -1.7 | -1.1 | -1.1 | -1.1 |
| Payments of capital leases | 0.0 | -0.1 | -0.1 | -0.1 | -0.1 | -0.1 | -0.1 | -0.1 |
| Payments of dividends to stockholders | -2.5 | -2.5 | | | | | | |
| Repurchase of common stock | | -1.7 | -1.8 | -0.3 | -4.5 | -9.3 | -11.7 | -15.2 |
| Net cash used in financing activities | -4.3 | -96.6 | -5.0 | 1.6 | -7.1 | -11.6 | -12.0 | -17.5 |
| Foreign-currency effect on cash, cash equivalents, and restricted cash | 0.4 | | | | 0.0 | | | |
| Net increase in cash, cash equivalents, and restricted cash | 20.5 | | | | 58.4 | | | |
| |
| Non-cash investing and financing activities | | | | | | | | |
| Change in patent assets purchased and accrued but not paid | | 0.4 | -0.4 | 0.1 | 0.3 | 0.9 | -0.3 | 0.0 |
| Change in fixed assets purchased and accrued but not paid | | | | | 0.0 | | | |
| |
| Restricted Cash and Cash Equivalents, Current | | | | | | | | |
| Restricted Cash and Cash Equivalents, Noncurrent | | | | | | | | |