Quarterly Financial Data Quarterly Financial Data Level 4 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data (Unaudited) [Abstract]
Revenue	$ 769,383		$ 714,526		$ 754,354		$ 748,117		$ 783,444		$ 718,314		$ 746,760		$ 745,493		$ 2,986,380	$ 2,994,011	$ 2,550,466
Costs and expenses	(581,942)		(573,723)		(588,096)		(570,674)		(578,142)		(570,030)		(590,719)		(579,435)		(2,314,435)	(2,318,326)	(2,001,419)
Gross profits	187,441		140,803		166,258		177,443		205,302		148,284		156,041		166,058		671,945	675,685	549,047
Operating income	157,035		124,548		127,581		141,115		220,281		135,119		144,730		107,419		550,279	607,549	387,656
Income from continuing operations before income taxes	113,699	[1]	74,045	[1]	84,489	[1]	98,118	[1]	177,591	[1]	91,735	[1]	69,316	[1]	63,958	[1]	370,351	402,600	245,206
Provision for income taxes	(41,249)		(26,118)		(31,007)		(36,653)		(90,982)		(74,934)		(37,357)		(22,707)		135,027	225,980	93,024
Net income from continuing operations	72,450		47,927		53,482		61,465		86,609		16,801		31,959		41,251		235,324	176,620	152,182
Net loss from discontinued operations, net of tax	0		0		(390)		0		1,340		884		(178)		140		(390)	2,186	406
Net income	72,450		47,927		53,092		61,465		87,949		17,685		31,781		41,391		234,934	178,806	152,588
Net income attributable to noncontrolling interests	(96)		(479)		(497)		(90)		(155)		(34)		(5,859)		(289)		(1,162)	(6,337)	(5,256)
Net income attributable to common stockholders	$ 72,354		$ 47,448		$ 52,595		$ 61,375		$ 87,794		$ 17,651		$ 25,922		$ 41,102		$ 233,772	$ 172,469	$ 147,332
Basic — EPS	$ 0.37	[2]	$ 0.24	[2]	$ 0.26	[2]	$ 0.30	[2]	$ 0.42	[2]	$ 0.08	[2]	$ 0.12	[2]	$ 0.19	[2]	$ 1.17	$ 0.82	$ 0.70
Earnings per share, diluted	$ 0.36	[2]	$ 0.23	[2]	$ 0.25	[2]	$ 0.30	[2]	$ 0.42	[2]	$ 0.08	[2]	$ 0.12	[2]	$ 0.19	[2]	$ 1.14	$ 0.81	$ 0.68

[1] Includes (Losses) gains on divestitures and impairment charges, net, as described in Note 19.

[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.