CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows from Operating Activities:
Net income	$ 92.6	$ 78.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	43.0	46.6
Stock-based compensation	16.9	23.3
Other	3.5	8.5
Changes in operating assets and liabilities:
Accounts receivable	40.5	1.0
Prepaid expenses and income taxes	13.5	(5.3)
Accounts payable	(0.2)	(21.0)
Accrued payroll and contract professional pay	(0.1)	0.5
Income taxes payable	16.7	10.0
Operating lease right of use assets	14.4	13.9
Operating lease liabilities	(14.6)	(13.7)
Other	24.0	(1.3)
Net Cash Provided by Operating Activities	250.2	140.5
Cash Flows from Investing Activities:
Cash paid for property and equipment	(22.6)	(15.9)
Cash paid for acquisitions, net of cash acquired	(85.5)	(48.5)
Other	(0.3)	(0.9)
Net cash used in investing activities	(108.4)	(65.3)
Cash Flows from Financing Activities:
Proceeds from long-term debt	65.5	50.0
Principal payments of long-term debt	(65.5)	(127.0)
Payments of Debt Issuance Costs	(1.3)	0.0
Proceeds from option exercises and employee stock purchase plan	5.9	6.9
Payment of employment taxes related to release of restricted stock awards	(5.9)	(6.8)
Payments for Repurchase of Common Stock	(27.9)	0.0
Net Cash provided by (used in) Financing Activities	(29.2)	(76.9)
Effect of exchange rate changes on cash and cash equivalents	0.1	0.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	112.7	(1.7)
Cash and Cash Equivalents at Beginning of Year	95.2	41.8
Cash and Cash Equivalents at End of Period	207.9	40.1
Supplemental Disclosure of Cash Flow Information:
Income taxes	5.3	21.0
Interest	19.7	25.4
Supplemental Disclosure of Non-Cash Transactions:
Unpaid portion of additions to property and equipment	4.2	1.1
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 10.4	$ 7.6