Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenue	$ 1,028,417	$ 891,898	$ 837,492	$ 796,268	$ 831,343	$ 790,125	$ 788,573	$ 795,084	$ 3,554,075		$ 3,205,125		$ 3,211,522
Cost of revenue	729,845	608,191	565,296	502,891	518,920	467,805	468,227	467,187	2,406,223		1,922,139
Operating expenses	282,973	272,380	255,477	521,954	304,042	341,870	287,312	322,620	1,332,784		1,255,844
Total	15,599	11,327	16,719	(228,577)	8,381	(19,550)	33,034	5,277	(184,932)		27,142		188,121
Provision (benefit) for income taxes	(813)	554	17,016	(10,030)	344	(24,895)	3,724	7,820	6,727		(13,007)		6,416
Income from continuing operations	16,412	10,773	(297)	(218,547)	8,037	5,345	29,310	(2,543)	(191,659)		40,149
Income from discontinued operations, net of tax	2,467	616	(3,032)	10,064	168,659	(8,470)	(5,613)	(116)	10,115		154,460		60,106
Net (loss) income	$ 18,879	$ 11,389	$ (3,329)	$ (208,483)	$ 176,696	$ (3,125)	$ 23,697	$ (2,659)	$ (181,544)		$ 194,609		$ 241,811
Basic earnings per share
Continuing operations (in dollars per share)	$ 0.10	$ 0.06	$ 0	$ (1.28)	$ 0.05	$ 0.03	$ 0.17	$ (0.01)	$ (1.12)	[1]	$ 0.23	[1]	$ 0.97	[1]
Discontinued operations (in dollars per share)	0.01	0	(0.02)	0.06	0.99	(0.05)	(0.03)	0	0.06	[1]	0.88	[1]	0.32	[1]
Net income (in dollars per share)	0.11	0.07	(0.02)	(1.22)	1.04	(0.02)	0.13	(0.01)	(1.06)	[1]	1.10	[1]	1.29	[1]
Diluted earnings per share
Continuing operations (in dollars per share)	0.09	0.06	0	(1.28)	0.05	0.03	0.16	(0.01)	(1.12)	[1]	0.23	[1]	0.96	[1]
Discontinued operations (in dollars per share)	0.01	0	(0.02)	0.06	0.98	(0.05)	(0.03)	0	0.06	[1]	0.87	[1]	0.32	[1]
Net income (in dollars per share)	$ 0.11	$ 0.07	$ (0.02)	$ (1.22)	$ 1.03	$ (0.02)	$ 0.13	$ (0.01)	$ (1.06)	[1]	$ 1.10	[1]	$ 1.28	[1]
Benefit for the correction of tax balances in certain domestic and international tax jurisdictions	$ 5,000								$ 5,000

[1] The sum of the earnings per share amounts may not equal the totals due to rounding.