Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net income	$ 127,243	$ 82,554
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	14,304	16,253
Amortization and impairment of other intangible assets	3,713	4,322
Acquisition-related contingent consideration	186	232
Provision for doubtful accounts	6,260	8,710
Non-cash share-based compensation	10,207	8,563
Amortization of debt discount and issuance costs	5,748	993
Other	225	798
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, billed and unbilled	(186,854)	(99,299)
Notes receivable	8,343	4,214
Prepaid expenses and other assets	(1,953)	(4,151)
Accounts payable, accrued expenses and other	(11,606)	352
Income taxes	24,424	13,143
Accrued compensation	(55,183)	(58,547)
Billings in excess of services provided	505	(12,722)
Net cash used in operating activities	(54,438)	(34,585)
Investing activities
Purchases of property and equipment	(20,661)	(16,220)
Other	69	689
Net cash used in investing activities	(20,592)	(15,531)
Financing activities
Proceeds from lines of credit	20,000
Repayments of lines of credit		(25,000)
Deposits	1,014	2,602
Purchase and retirement of common stock	(66,893)	(14,220)
Net issuance of common stock under equity compensation plans	1,009	18,740
Payments for business acquisition liabilities	(2,282)	(3,029)
Net cash used in financing activities	(47,152)	(20,907)
Effect of exchange rate changes on cash and cash equivalents	(781)	(2,382)
Net decrease in cash and cash equivalents	(122,963)	(73,405)
Cash and cash equivalents, beginning of period	312,069	189,961
Cash and cash equivalents, end of period	189,106	116,556
Supplemental cash flow disclosures
Cash paid for interest	3,467	13,020
Cash paid for income taxes, net of refunds	16,820	16,137
Non-cash investing and financing activities:
Issuance of stock units under incentive compensation plans	1,346	1,059
Purchase and retirement of common stock not yet paid	$ 3,322	$ 0