CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net income	$ 52,091	$ 30,181	$ 37,125
Adjustments to reconcile net income to net cash provided by operations:
Depreciation	6,398	5,430	4,447
Amortization	23,453	22,857	16,151
Loss on extinguishment of debt	28,996	4,537	0
Deferred income taxes	(12,662)	(1,588)	2,041
Non-cash stock compensation and retirement savings plan contributions	21,554	19,146	17,425
Amortization of debt issuance costs and discounts	11,014	6,855	4,667
Adjustment to fair value of contingent consideration for purchase of business	198	9,519	301
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(34,451)	8,237	(3,402)
Other assets	(3,475)	1,821	(7,677)
Accounts payable	56	861	(1,356)
Other liabilities	(8,256)	10,104	8,243
Net cash provided by operating activities	84,916	117,960	77,965
INVESTING ACTIVITIES
Purchase of property and equipment	(9,244)	(5,266)	(8,082)
Capitalization of internally developed software costs	(960)	(1,465)	(1,174)
Purchase of businesses, net of cash acquired	(108,848)	(91,883)	(11,143)
Net cash used in investing activities	(119,052)	(98,614)	(20,399)
FINANCING ACTIVITIES
Proceeds from issuance of convertible notes	380,000	230,000	0
Payment for convertible notes issuance costs	(10,540)	(7,253)	0
Purchase of hedges related to issuance of convertible notes	(66,120)	(48,944)	0
Proceeds from issuance of warrants related to issuance of convertible notes	23,408	22,218	0
Payments for repurchase of convertible notes	(368,664)	(180,420)	0
Proceeds from sale of hedges related to repurchase of convertible notes	381,290	50,062	0
Repurchase of warrants related to repurchase of convertible notes	(303,896)	(43,028)	0
Payment for credit facility financing fees	(633)	0	0
Proceeds from line of credit	74,000	28,000	0
Payments on line of credit	(74,000)	(28,000)	0
Payment of contingent consideration for purchase of business	(24,128)	(2,820)	(4,281)
Proceeds from the sale of stock through the Employee Stock Purchase Plan	631	310	178
Purchases of treasury stock	(21,724)	(19,573)	(20,612)
Remittance of taxes withheld as part of a net share settlement of restricted stock vesting	(13,463)	(8,028)	(7,336)
Net cash used in financing activities	(23,839)	(7,476)	(32,051)
Effect of exchange rate on cash and cash equivalents	(819)	606	229
Change in cash and cash equivalents	(58,794)	12,476	25,744
Cash and cash equivalents at beginning of period	83,204	70,728	44,984
Cash and cash equivalents at end of period	24,410	83,204	70,728
Supplemental disclosures:
Cash paid for income taxes	16,122	5,256	7,405
Cash paid for interest	3,988	3,411	3,674
Non-cash activities:
Stock issued for purchase of businesses	6,244	8,729	1,294
Issuance of shares for repurchase of convertible notes	243,167	0	0
Liability incurred for purchase of property and equipment	$ 144	$ 503	$ 1,851