Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 62,991	$ 78,210
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	24,428	18,492
Non-cash interest expense and other	1,134	1,277
Write-off of fees on the prior credit facilities	0	574
Change in fair value of contingent consideration	(2,158)	19
Increase in allowances for doubtful accounts and sales credits	4,978	4,809
Provision for deferred income taxes	(10,328)	(7,173)
Share-based compensation	8,888	6,145
Loss on disposal or sale of fixed assets	39	39
Amortization of discount on investments	(229)	(62)
Non-cash lease expense	(106)
Changes in assets and liabilities, net of effects from acquisitions:
Accounts receivable	12,427	13,830
Accounts receivable, subcontractor	84	6,355
Income taxes receivable	(1,673)	13,986
Prepaid expenses	(1,523)	(2,012)
Other current assets	583	(613)
Other assets	(8,763)	556
Accounts payable and accrued expenses	(29,471)	(8,954)
Accrued compensation and benefits	11,774	5,468
Other liabilities	(5,852)	(6,588)
Deferred revenue	(2,025)	1,573
Restricted investments balance	93	7
Net cash provided by operating activities	65,291	125,938
Cash flows from investing activities:
Purchase and development of fixed assets	(15,532)	(16,457)
Purchase of investments	(13,281)	(6,742)
Proceeds from maturity of investments	22,670	8,200
Payments to fund deferred compensation plan	(5,279)	(4,724)
Cash paid for acquisitions, net of cash received	(228,149)	(218,047)
Cash paid for other intangibles	(1,120)	(1,180)
Net cash used in investing activities	(240,691)	(238,950)
Cash flows from financing activities:
Proceeds from term loans	150,000	0
Payments on revolving credit facility	(25,000)	(40,000)
Proceeds from revolving credit facility	101,000	195,000
Repurchase of common stock	(18,705)	(20,891)
Payment of financing costs	(777)	(2,331)
Earn-out payments for prior acquisitions	(5,700)	(1,713)
Cash paid for shares withheld for taxes	(11,533)	(11,408)
Net cash provided by financing activities	189,285	118,657
Effect of exchange rate changes on cash	(190)	72
Net increase in cash, cash equivalents and restricted cash	13,695	5,717
Cash, cash equivalents and restricted cash at the beginning of period	84,324	98,894
Cash, cash equivalents and restricted cash at the end of period	98,019	104,611
Supplemental disclosures of cash flow information:
Cash paid for amounts included in the measurement of operating lease liabilities	8,694
Cash paid for interest (net of $230 and $193 capitalized for the six months ended June 30, 2019 and 2018, respectively)	11,714	10,167
Cash paid for income taxes	27,369	14,405
Acquisitions:
Fair value of tangible assets acquired in acquisitions, net of cash and restricted cash received	27,674	23,577
Goodwill	149,941	98,538
Intangible assets	96,180	122,110
Liabilities assumed	(33,524)	(16,078)
Earn-out liabilities	(12,122)	(10,100)
Supplemental disclosures of non-cash investing and financing activities:
Purchase of fixed assets recorded in accounts payable and accrued expenses	$ 2,352	$ 1,800