Summary of Significant Accounting Policies Summary of Significant Accounting Policies, Revenue Recognition (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 802,965	$ 798,212
Gross profit	179,044	191,834
Costs of revenue	(623,921)	(606,378)
Corporate general and administrative expenses	(31,813)	(42,978)
Gains on divestitures and impairment charges, net	(4,545)	1,878
Operating income	151,776	146,978
Interest expense	(44,351)	(47,390)
Loss on early extinguishment of debt, net	139	0
Nonoperating Income (Expense)	(1,247)	720
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	106,039	100,308
Income Tax Expense (Benefit)	24,038	21,095
Net income	82,001	79,213
Net income attributable to noncontrolling interests	60	(110)
Net income attributable to common stockholders	$ 81,941	$ 79,323
Net income attributable to common stockholders, basic	$ 0.45	$ 0.44
Net income attributable to common stockholders, diluted	$ 0.45	$ 0.43
Change in amounts due for unfulfilled performance obligations	$ (2,555)	$ (6,178)