| In millions, except per share items | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities: | | | | | | | | |
| Net income | 56.4 | 64.1 | 48.9 | 32.2 | 62.4 | 68.6 | 57.8 | 37.3 |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation | 51.6 | 52.1 | 57.8 | 56.5 | 49.6 | 44.5 | 46.3 | 43.1 |
| Amortization of intangibles | 14.0 | 16.6 | 15.5 | 21.1 | 19.4 | 14.2 | 14.4 | 14.9 |
| Amortization of deferred grants | -1.1 | -0.4 | -0.7 | -0.7 | -0.8 | -1.0 | -1.3 | -1.1 |
| Impairment losses | 41.6 | 1.7 | 9.4 | 5.4 | | | | |
| Unrealized foreign currency transaction (gains) losses, net | 2.1 | -2.3 | -0.8 | -4.7 | -1.1 | 0.3 | 0.1 | 6.3 |
| Stock-based compensation expense | 10.7 | 7.4 | 7.5 | 7.6 | 10.8 | 8.7 | 6.4 | 4.9 |
| Deferred income tax provision (benefit) | -5.6 | 0.3 | -1.5 | 7.9 | 2.3 | 2.5 | 4.9 | -0.4 |
| Bad debt expense (reversals) | | | | | | | -0.2 | 0.5 |
| Unrealized (gains) losses and premiums on financial instruments, net | 1.1 | -1.1 | 0.8 | -0.1 | 0.5 | 1.0 | | |
| Other | 1.6 | 0.8 | 0.5 | 0.0 | 0.0 | 0.2 | 0.0 | -0.1 |
| Changes in assets and liabilities, net of acquisitions: | | | | | | | | |
| Receivables, net | -9.3 | -40.2 | -8.2 | -10.2 | -32.9 | 2.5 | -40.3 | -22.1 |
| Prepaid expenses | -0.1 | -0.3 | -1.7 | -0.2 | -3.6 | -3.0 | 0.3 | -3.9 |
| Other current assets | -0.3 | -0.1 | -0.7 | -1.4 | -3.4 | -7.0 | -6.7 | -1.2 |
| Deferred charges and other assets | -4.7 | -12.2 | -13.6 | -0.9 | -1.3 | 2.0 | 3.5 | -2.8 |
| Accounts payable | -3.6 | 2.1 | -1.6 | 7.3 | -2.9 | -0.1 | 2.0 | -1.3 |
| Income taxes receivable / payable | -3.0 | -0.1 | -1.1 | 1.1 | 5.0 | -5.7 | | |
| Accrued employee compensation and benefits | 31.1 | 9.4 | -6.4 | 5.1 | 15.7 | -1.5 | 5.2 | 9.1 |
| Other accrued expenses and current liabilities | -2.4 | 3.5 | 0.4 | -5.5 | 5.1 | -1.6 | -5.0 | -2.0 |
| Deferred revenue and customer liabilities | -2.8 | -4.5 | -1.6 | -5.9 | 6.3 | | | |
| Other long-term liabilities | 1.6 | 3.9 | 5.1 | 20.0 | 2.9 | -2.4 | 2.1 | 0.9 |
| Operating lease assets and liabilities | -2.8 | 0.8 | | | | | | |
| Net cash provided by operating activities | 175.7 | 101.3 | 109.1 | 134.8 | 132.8 | 120.9 | 94.3 | 86.2 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Capital expenditures | -52.7 | -38.7 | -46.9 | -63.3 | -78.3 | -49.7 | -44.7 | -59.2 |
| Cash paid for business acquisitions, net of cash acquired | -88.5 | -3.1 | -78.4 | -9.1 | -205.3 | -9.4 | | |
| Purchase of intangible assets | | -0.3 | -8.2 | -4.8 | 0.0 | | | |
| Other | 1.8 | 0.3 | 1.5 | 0.1 | 0.6 | 0.6 | | |
| Net cash (used for) investing activities | -139.4 | -40.6 | -136.9 | -87.3 | -272.8 | -57.0 | -40.9 | -59.4 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Payments of long-term debt | -101.0 | -58.0 | -231.0 | | -19.0 | -10.0 | -23.0 | -25.0 |
| Proceeds from issuance of long-term debt | 91.0 | 29.0 | 58.0 | 8.0 | 216.0 | 5.0 | | 32.0 |
| Cash paid for repurchase of common stock | -52.2 | -30.3 | | | -11.1 | -20.9 | -12.6 | -5.5 |
| Taxes paid related to net share settlement of equity awards | -1.8 | -3.2 | -3.7 | -3.9 | -4.9 | -3.3 | -0.4 | -0.2 |
| Net cash (used for) financing activities | -64.0 | -63.6 | -176.7 | -1.5 | 179.7 | -29.8 | -35.8 | 1.6 |
| Effects of exchange rates on cash, cash equivalents and restricted cash | 2.8 | 1.9 | -10.1 | 31.2 | -8.5 | | | |
| |
| Supplemental disclosures of cash flow information: | | | | | | | | |
| Cash paid during period for interest | 1.4 | 3.5 | 3.9 | 6.7 | 4.0 | 1.5 | 1.7 | 2.1 |
| Cash paid during period for income taxes | 32.8 | 24.0 | 19.6 | 24.3 | 18.8 | 30.5 | 16.6 | 16.9 |
| Non-cash transactions: | | | | | | | | |
| Capital expenditures incurred but not yet paid | 6.1 | 6.0 | 1.9 | 6.1 | 10.7 | 4.9 | 5.5 | 6.0 |
| Property and equipment acquired under grant agreement | 1.6 | | | | | | | |