Summary of Significant Accounting Policies Revenue Recognition Impact (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 794,482	$ 777,710
Costs and expenses	(598,720)	(600,471)
Gross Profit	195,762	177,239
General and administrative expenses	(34,784)	(42,283)
Gains on divestitures and impairment charges, net	482	4,935
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	2,232	0
Operating income	163,692	139,891
Interest expense	(43,576)	(40,636)
Loss on early extinguishment of debt, net	(10,131)	0
Other income (expense), net	384	(729)
Income before income taxes	110,369	98,526
(Provision for) benefit from income taxes	(28,321)	76,223
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	82,048	174,749
Net income attributable to noncontrolling interests	(60)	(47)
Net Income (Loss) Attributable to Parent	$ 81,988	$ 174,702
Basic	$ 0.44	$ 0.93
Net income attributable to common stockholders, diluted	$ 0.43	$ 0.91
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 557
Costs and expenses	(7,267)
Gross Profit	(6,710)
General and administrative expenses	0
Gains on divestitures and impairment charges, net	0
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	0
Operating income	(6,710)
Interest expense	0
Loss on early extinguishment of debt, net	0
Other income (expense), net	0
Income before income taxes	(6,710)
(Provision for) benefit from income taxes	1,724
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(4,986)
Net income attributable to noncontrolling interests	0
Net Income (Loss) Attributable to Parent	$ (4,986)
Basic	$ (0.03)
Net income attributable to common stockholders, diluted	$ (0.03)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 795,039
Costs and expenses	(605,987)
Gross Profit	189,052
General and administrative expenses	(34,784)
Gains on divestitures and impairment charges, net	482
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	2,232
Operating income	156,982
Interest expense	(43,576)
Loss on early extinguishment of debt, net	(10,131)
Other income (expense), net	384
Income before income taxes	103,659
(Provision for) benefit from income taxes	(26,597)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	77,062
Net income attributable to noncontrolling interests	(60)
Net Income (Loss) Attributable to Parent	$ 77,002
Basic	$ 0.42
Net income attributable to common stockholders, diluted	$ 0.41