Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net income	$ 104,921	$ 127,243
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	15,707	14,304
Amortization and impairment of other intangible assets	4,645	3,713
Acquisition-related contingent consideration	1,120	186
Provision for doubtful accounts	11,624	6,260
Share-based compensation	12,147	10,207
Amortization of debt discount and issuance costs	5,987	5,748
Deferred income taxes	4,128	966
Other	13	225
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, billed and unbilled	(42,804)	(186,854)
Notes receivable	5,993	8,343
Prepaid expenses and other assets	8,979	(1,953)
Accounts payable, accrued expenses and other	2,230	(11,606)
Income taxes	(2,344)	23,458
Accrued compensation	(107,217)	(55,183)
Billings in excess of services provided	4,285	505
Net cash provided by (used in) operating activities	29,414	(54,438)
Investing activities
Purchases of property and equipment	(13,899)	(20,661)
Other	14	69
Net cash used in investing activities	(13,885)	(20,592)
Financing activities
Borrowings under revolving line of credit	90,000	25,000
Repayments under revolving line of credit	(55,000)	(5,000)
Purchase and retirement of common stock	(99,678)	(66,893)
Net issuance of common stock under equity compensation plans	(6,523)	1,009
Payments for business acquisition liabilities	(3,948)	(2,282)
Deposits and other	5,098	1,014
Net cash used in financing activities	(70,051)	(47,152)
Effect of exchange rate changes on cash and cash equivalents	(10,645)	(781)
Net decrease in cash and cash equivalents	(65,167)	(122,963)
Cash and cash equivalents, beginning of period	369,373	312,069
Cash and cash equivalents, end of period	304,206	189,106
Supplemental cash flow disclosures
Cash paid for interest	3,668	3,467
Cash paid for income taxes, net of refunds	29,150	16,820
Non-cash investing and financing activities:
Issuance of stock units under incentive compensation plans	2,314	1,346
Purchase and retirement of common stock not yet paid	$ 1,829	$ 3,322