Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 74,952	$ 58,098	$ 60,345
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation expense	28,826	27,742	23,612
Amortization expense	8,960	11,507	8,613
Share-based compensation expense	13,037	13,071	10,328
Deferred income taxes	(16,463)	(2,154)	13,807
Allowance for doubtful accounts receivable	7,755	8,815	2,578
Contingent acquisition liability adjustments, net	2,213	1,330	(13,047)
Other, net	3,113	(159)	2,598
Changes in assets and liabilities (net of acquisitions):
Accounts receivable	(11,773)	(49,972)	(27,875)
Prepaid expenses and other assets	(6,712)	4,189	(5,575)
Accounts payable	1,058	1,630	(2,271)
Accrued liabilities	1,158	874	476
Accrued compensation-related costs	(10,589)	14,447	6,875
Income taxes payable	3,248	5,773	(4,081)
Other liabilities	5,452	14,836	6,696
Net cash provided by operating activities	104,235	110,027	83,079
Cash flows from investing activities:
Purchases of property and equipment	(38,650)	(28,665)	(39,094)
Acquisitions of businesses, net of cash acquired	(5,000)	(15,426)	(64,037)
Other acquisition payments		(5,500)
Payments of acquisition liabilities		(1,165)	(13,546)
Other, net	(812)	(770)	(735)
Net cash used in investing activities	(44,462)	(51,526)	(117,412)
Cash flows from financing activities:
Issuances of common stock	3,919	4,299	5,974
Repurchases of common stock	(43,005)	(25,057)	(24,021)
Payments of contingent acquisition liabilities	(10,330)	(828)	(4,592)
Repayments to banks	(457,200)	(410,197)	(332,455)
Borrowings from banks	452,524	375,708	397,320
Payments of debt issuance costs	(1,297)
Other, net	(5,009)	(2,723)	(1,415)
Net cash (used in) provided by financing activities	(60,398)	(58,798)	40,811
Effect of exchange rate changes on cash and cash equivalents	783	(307)	(231)
Net increase (decrease) in cash and cash equivalents	158	(604)	6,247
Cash and cash equivalents at beginning of the period	8,291	8,895	2,648
Cash and cash equivalents at end of the period	8,449	8,291	8,895
Supplemental Consolidated Cash Flow Information
Interest paid	4,237	3,692	3,183
Income taxes paid, net of refunds	15,553	$ 22,752	$ 16,733
Impact of Tax Cuts and Jobs Act on deferred income tax balances	$ 29,900