Summary of Significant Accounting Policies Summary of Significant Accounting Policies, Revenue Recognition (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
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 970,268		$ 918,241		$ 820,035		$ 802,965		$ 850,760		$ 769,241		$ 812,572		$ 798,212		$ 3,511,509	$ 3,230,785	$ 3,190,174
Gross profit	315,360		263,656		218,767		179,044		217,868		159,732		191,146		191,834		976,827	760,580	760,322
Costs of revenue	(654,908)		(654,585)		(601,268)		(623,921)		(632,892)		(609,509)		(621,426)		(606,378)		(2,534,682)	(2,470,205)	(2,429,852)
Corporate general and administrative expenses																	(141,066)	(126,886)	(145,596)
Gains on divestitures and impairment charges, net																	7,009	32,919	15,933
Operating income	285,446		223,213		182,335		151,776		240,945		128,585		150,105		146,978		842,770	666,613	630,659
Interest expense																	(163,063)	(185,843)	(181,556)
Losses on early extinguishment of debt, net																	(18,428)	(16,637)	(10,131)
Nonoperating Income (Expense)																	781	299	2,760
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	249,455	[1]	164,843	[1]	141,723	[1]	106,039	[1]	195,172	[1]	72,869	[1]	96,083	[1]	100,308	[1]	662,060	464,432	441,732
Income Tax Expense (Benefit)	(48,364)		(37,351)		(36,170)		(24,038)		(47,999)		(1,997)		(23,570)		(21,095)		(145,923)	(94,661)	5,826
Net income	201,091		127,492		105,553		82,001		147,173		70,872		72,513		79,213		516,137	369,771	447,558
Net income attributable to noncontrolling interests	(48)		(77)		(45)		(60)		(21)		(80)		(184)		110		(230)	(175)	(350)
Net income attributable to common stockholders	$ 201,043		$ 127,415		$ 105,508		$ 81,941		$ 147,152		$ 70,792		$ 72,329		$ 79,323		$ 515,907	$ 369,596	$ 447,208
Net income attributable to common stockholders, basic	$ 1.17	[2]	$ 0.72	[2]	$ 0.59	[2]	$ 0.45	[2]	$ 0.81	[2]	$ 0.39	[2]	$ 0.40	[2]	$ 0.44	[2]	$ 2.92	$ 2.03	$ 2.45
Net income attributable to common stockholders, diluted	$ 1.15	[2]	$ 0.72	[2]	$ 0.59	[2]	$ 0.45	[2]	$ 0.79	[2]	$ 0.38	[2]	$ 0.39	[2]	$ 0.43	[2]	$ 2.88	$ 1.99	$ 2.39
Change in amounts due for unfulfilled performance obligations																	$ (55,269)	$ (10,223)	$ (546,554)

[1] Includes Gains (losses) on divestitures and impairment charges, net, as described in Note 16.

[2] Net income per share is computed independently for each of the quarters presented. Therefore, the sum of the quarters’ net income per share may not equal the total computed for the year.