Selected Unaudited Quarterly Financial Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly Financial Information [Line Items]
Revenues	$ 816,175		$ 879,894		$ 849,801		$ 899,240		$ 539,622	$ 732,095	$ 627,144	$ 504,882	$ 3,445,110	$ 2,403,743	$ 3,281,790
Operating income	31,430		35,216		83,779		100,298		59,273	84,303	98,142	73,187	250,723	314,905	279,349
Income from continuing operations, less noncontrolling interest	9,302		9,764		63,718		68,758		45,480	60,833	78,691	51,562	151,542	236,566	206,158
Income (loss) from discontinued operations, net of tax	(19,271)		1,187		3,610		1,662		(592)	(40,030)	(2,657)	8,379	(12,812)	(34,900)	180,898
Net income	$ (9,969)	[1]	$ 10,951	[1]	$ 67,328	[1]	$ 70,420	[1]	$ 44,888	$ 20,803	$ 76,034	$ 59,941	$ 138,730	$ 201,666	$ 387,056
Basic earnings per common share:
Income from continuing operations, less noncontrolling interest	$ 0.04		$ 0.04		$ 0.27		$ 0.29		$ 0.20	$ 0.26	$ 0.34	$ 0.22	$ 0.65	$ 1.02	$ 0.90
Income (loss) from discontinued operations, net of tax	$ (0.08)		$ 0.01		$ 0.02		$ 0.01			$ (0.17)	$ (0.01)	$ 0.04	$ (0.05)	$ (0.15)	$ 0.79
Net income	$ (0.04)		$ 0.05		$ 0.29		$ 0.30		$ 0.19	$ 0.09	$ 0.33	$ 0.26	$ 0.59	$ 0.87	$ 1.69
Diluted earnings per common share:
Income from continuing operations, less noncontrolling interest	$ 0.04		$ 0.04		$ 0.27		$ 0.29		$ 0.19	$ 0.26	$ 0.34	$ 0.22	$ 0.64	$ 1.00	$ 0.88
Income (loss) from discontinued operations, net of tax	$ (0.08)		$ 0.01		$ 0.02		$ 0.01			$ (0.17)	$ (0.01)	$ 0.04	$ (0.05)	$ (0.15)	$ 0.78
Net income	$ (0.04)		$ 0.05		$ 0.28		$ 0.30		$ 0.19	$ 0.09	$ 0.32	$ 0.26	$ 0.59	$ 0.85	$ 1.66

[1] See Note 2 for discussion on discontinued operations and other items.