Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenues	$ 604,593	$ 551,274
Operating expenses
Direct cost of revenues	402,247	349,066
Selling, general and administrative expenses	126,959	113,185
Amortization of other intangible assets	2,331	1,861
Operating expenses	531,537	464,112
Operating income	73,056	87,162
Other income (expense)
Interest income and other	5,017	159
Interest expense	(4,861)	(4,746)
Other income (expense)	156	(4,587)
Income before income tax provision	73,212	82,575
Income tax provision	16,465	19,930
Net income	$ 56,747	$ 62,645
Earnings per common share — basic (in dollars per share)	$ 1.56	$ 1.69
Earnings per common share — diluted (in dollars per share)	$ 1.49	$ 1.64
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments, net of tax expense of $0	$ (31,102)	$ 5,223
Total other comprehensive income (loss), net of tax	(31,102)	5,223
Comprehensive income	$ 25,645	$ 67,868