Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 12,965	$ 34,122
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	20,234	11,710
Non-cash interest expense and other	1,911	543
Change in fair value of contingent consideration	200	(700)
Increase in allowance for credit losses and sales credits	4,735	2,608
Provision for deferred income taxes	733	(9,036)
Share-based compensation	4,927	5,186
Loss on disposal or sale of fixed assets	3,266	4
Amortization of discount on investments	(50)	(120)
Net gain on deferred compensation balances	(240)	0
Non-cash lease expense	(179)	(92)
Changes in assets and liabilities, net of effects from acquisitions:
Accounts receivable	(5,786)	(1,500)
Accounts receivable, subcontractor	(3,224)	(5,465)
Income taxes receivable	5,984	799
Prepaid expenses	(7,663)	(5,387)
Other current assets	3,463	(1,783)
Other assets	2,409	(6,202)
Accounts payable and accrued expenses	15,836	2,949
Accrued compensation and benefits	(2,031)	330
Other liabilities	(6,894)	9,630
Deferred revenue	748	(1,418)
Restricted investments balance	21	36
Net cash provided by operating activities	51,365	36,214
Cash flows from investing activities:
Purchase and development of fixed assets	(13,571)	(7,388)
Purchase of investments	(4,479)	(7,362)
Proceeds from maturity of investments	9,600	11,700
Payments to fund deferred compensation plan	(5,471)	(3,583)
Purchase of convertible promissory note	(490)	0
Cash paid for acquisitions, net of cash and restricted cash received	(476,392)	(29,525)
Cash paid for other intangibles	(1,400)	(90)
Cash received for working capital adjustments for prior year acquisitions	66	0
Net cash used in investing activities	(492,137)	(36,248)
Cash flows from financing activities:
Proceeds from term loans	250,000	0
Proceeds from revolving credit facility	225,000	30,000
Repurchase of common stock	0	(17,930)
Payment of financing costs	(3,899)	0
Earn-out payments for prior acquisitions	(10,622)	0
Cash paid for shares withheld for taxes	(4,353)	(10,280)
Net cash provided by financing activities	456,126	1,790
Effect of exchange rate changes on cash	(47)	(101)
Net increase in cash, cash equivalents and restricted cash	15,307	1,655
Cash, cash equivalents and restricted cash at the beginning of period	153,962	84,324
Cash, cash equivalents and restricted cash at the end of period	169,269	85,979
Supplemental disclosures of cash flow information:
Cash paid for amounts included in the measurement of operating lease liabilities	4,734	4,338
Cash paid for interest (net of $159 and $102 capitalized for the three months ended March 31, 2020 and 2019, respectively)	1,898	1,524
Cash paid for income taxes	45	4,192
Acquisitions:
Fair value of tangible assets acquired in acquisitions, net of cash and restricted cash received	37,240	1,041
Goodwill	255,974	26,494
Intangible assets	252,000	6,880
Liabilities assumed	(68,822)	(3,390)
Earn-out liabilities	0	(1,500)
Net cash paid for acquisitions	476,392	29,525
Supplemental disclosures of non-cash investing and financing activities:
Purchase of fixed assets recorded in accounts payable and accrued expenses	$ 1,786	$ 2,566