Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	$ 668,574		$ 609,951		$ 625,505		$ 652,352		$ 629,421		$ 581,182		$ 597,372		$ 602,506		$ 2,556,382	$ 2,410,481	$ 2,316,040
Costs and expenses	(520,755)		(493,896)		(499,467)		(492,695)		(481,610)		(460,429)		(469,741)		(475,488)		(2,006,813)	(1,887,268)	(1,839,538)
Gross profits	147,819		116,055		126,038		159,657		147,811		120,753		127,631		127,018		549,569	523,213	476,502
Operating income	87,995		83,296		89,114		127,765		103,806		95,176		99,689		101,118		388,170	399,789	363,699
Income before income taxes	49,682	[1]	45,882	[1]	56,143	[1]	94,012	[1]	46,749	[1]	63,925	[1]	63,574	[1]	71,435	[1]	245,719	245,683	225,636
Benefit (provision) for income taxes	(21,130)		(18,488)		(21,708)		(35,290)		(20,365)		(22,128)		(25,935)		(23,120)		96,615	91,548	79,404
Net income	28,552		27,394		34,435		58,722		26,384		41,797		37,639		48,315		149,104	154,135	146,232
Net income attributable to noncontrolling interests	(2,719)		(615)		(820)		(1,102)		(1)		(735)		(563)		(290)		(5,256)	(1,589)	(1,329)
Net income attributable to common stockholders	$ 25,833		$ 26,779		$ 33,615		$ 57,620		$ 26,383		$ 41,062		$ 37,076		$ 48,025		$ 143,848	$ 152,546	$ 144,903
Basic — EPS	$ 0.12	[2]	$ 0.13	[2]	$ 0.16	[2]	$ 0.27	[2]	$ 0.12	[2]	$ 0.19	[2]	$ 0.17	[2]	$ 0.22	[2]	$ 0.68	$ 0.71	$ 0.62
Diluted - EPS	$ 0.12	[2]	$ 0.12	[2]	$ 0.16	[2]	$ 0.27	[2]	$ 0.12	[2]	$ 0.19	[2]	$ 0.17	[2]	$ 0.22	[2]	$ 0.67	$ 0.70	$ 0.61

[1] Includes (Losses) gains on divestitures and impairment charges, net, as described in Note 20.

[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.