Summary of Significant Accounting Policies Revenue Recognition Impact (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 796,092	$ 773,242	$ 1,590,574	$ 1,550,952
Costs and expenses	(607,965)	(589,724)	(1,206,685)	(1,190,195)
Gross Profit	188,127	183,518	383,889	360,757
General and administrative expenses	(31,136)	(40,369)	(65,920)	(82,652)
Gains on divestitures and impairment charges, net	6,865	753	7,347	5,688
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	(1,902)	0	330	0
Operating income	161,954	143,902	325,646	283,793
Interest expense	(44,519)	(42,083)	(88,095)	(82,719)
Loss on early extinguishment of debt, net	0	0	(10,131)	0
Other income (expense), net	1,880	(301)	2,264	(1,030)
Income before income taxes	119,315	101,518	229,684	200,044
(Provision for) benefit from income taxes	(16,034)	(32,956)	(44,355)	43,267
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	103,281	68,562	185,329	243,311
Net income attributable to noncontrolling interests	(42)	(81)	(102)	(128)
Net Income (Loss) Attributable to Parent	$ 103,239	$ 68,481	$ 185,227	$ 243,183
Basic	$ 0.57	$ 0.37	$ 1.01	$ 1.29
Net income attributable to common stockholders, diluted	$ 0.55	$ 0.36	$ 0.98	$ 1.26
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 461		$ 1,018
Costs and expenses	(6,685)		(13,952)
Gross Profit	(6,224)		(12,934)
General and administrative expenses			0
Gains on divestitures and impairment charges, net	0		0
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	0		0
Operating income	(6,224)		(12,934)
Interest expense			0
Loss on early extinguishment of debt, net	0		0
Other income (expense), net	0		0
Income before income taxes	(6,224)		(12,934)
(Provision for) benefit from income taxes	772		2,496
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(5,452)		(10,438)
Net income attributable to noncontrolling interests	0		0
Net Income (Loss) Attributable to Parent	$ (5,452)		$ (10,438)
Basic	$ (29.85)		$ (56.77)
Net income attributable to common stockholders, diluted	$ (29.13)		$ (55.36)
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 796,553		$ 1,591,592
Costs and expenses	(614,650)		(1,220,637)
Gross Profit	181,903		370,955
General and administrative expenses	(31,136)		(65,920)
Gains on divestitures and impairment charges, net	6,865		7,347
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	(1,902)		330
Operating income	155,730		312,712
Interest expense	(44,519)		(88,095)
Loss on early extinguishment of debt, net	0		(10,131)
Other income (expense), net	1,880		2,264
Income before income taxes	113,091		216,750
(Provision for) benefit from income taxes	(15,262)		(41,859)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	97,829		174,891
Net income attributable to noncontrolling interests	(42)		(102)
Net Income (Loss) Attributable to Parent	$ 97,787		$ 174,789
Basic	$ 535.42		$ 950.58
Net income attributable to common stockholders, diluted	$ 522.40		$ 927.03