CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities:
Net income	$ 48.7	$ 43.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	22.0	21.4
Stock-based compensation	10.3	8.7
Other	(1.0)	(1.7)
Changes in operating assets and liabilities:
Accounts receivable	30.3	(30.5)
Prepaid expenses and income taxes	3.0	7.9
Accounts payable	(10.0)	(3.9)
Accrued payroll and contract professional pay	19.3	9.1
Income taxes payable	9.9	5.7
Operating lease right of use assets	8.9	7.2
Operating lease liabilities	(9.5)	(7.4)
Other	(14.1)	0.4
Net cash provided by operating activities	119.8	64.1
Cash Flows from Investing Activities:
Cash paid for property and equipment	(9.3)	(15.3)
Cash paid for acquisitions, net of cash acquired	0.0	(85.5)
Other	(0.1)	(0.2)
Net cash used in investing activities	(9.4)	(101.0)
Cash Flows from Financing Activities:
Proceeds from long-term debt	0.0	65.5
Principal payments of long-term debt	0.0	(32.5)
Proceeds from option exercises and employee stock purchase plan	7.7	5.9
Payment of employment taxes related to release of restricted stock awards	(4.8)	(4.9)
Repurchase of common stock	0.0	(27.9)
Net cash provided by financing activities	2.9	6.1
Effect of Exchange Rate on Cash and Cash Equivalents	(1.2)	(0.4)
Net Increase (Decrease) in Cash and Cash Equivalents	112.1	(31.2)
Cash and Cash Equivalents at Beginning of Year	274.4	95.2
Cash and Cash Equivalents at End of Period	386.5	64.0
Supplemental Disclosure of Cash Flow Information Cash paid for:
Income Taxes Paid	2.6	1.2
Interest	2.4	4.7
Operating lease liabilities	8.8	8.4
Non-cash transactions —
Operating lease right of use assets obtained in exchange for operating lease liabilities	$ 0.3	$ 8.5