CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Accumulated Deficit	Noncontrolling Interest
Balance at Dec. 31, 2011	$ 1,680,042	$ 704	$ 3,645,332	$ 6,059	$ (206,937)	$ (2,007,922)	$ 242,806
Increase (Decrease) in Stockholders' Equity
Treasury stock purchased	(1,842)				(1,842)
Shares issued in employee stock purchase plan	888	1	887
Stock-based compensation, net of forfeitures	8,627	7	8,295				325
Income tax benefit from stock-based compensation expense	(1,730)		(1,730)
Net proceeds from sale of Partnership units, net of tax	85,122		49,202				35,920
Cash distribution to noncontrolling unitholders of the Partnership	(27,017)						(27,017)
Comprehensive income (loss):
Net income (loss)	(159,611)					(147,113)	(12,498)
Derivative gain (loss), net of reclassifications to earnings and tax	1,642			2,835			(1,193)
Adjustments from changes in ownership of Partnership	360			360
Amortization of terminated interest rate swaps, net of tax	7,833			7,833
Foreign currency translation adjustment	(4,759)			(4,759)
Balance at Jun. 30, 2012	1,589,555	712	3,701,986	12,328	(208,779)	(2,155,035)	238,343
Balance at Dec. 31, 2012	1,702,259	713	3,710,758	23,909	(209,359)	(2,047,408)	223,646
Increase (Decrease) in Stockholders' Equity
Treasury stock purchased	(3,515)				(3,515)
Options exercised	5,789	3	5,786
Shares issued in employee stock purchase plan	805		805
Stock-based compensation, net of forfeitures	8,387	7	8,035				345
Income tax benefit from stock-based compensation expense	867		867
Adjustments from changes in ownership of Partnership	(17,665)		31,573				(49,238)
Cash distribution to noncontrolling unitholders of the Partnership	(30,679)						(30,679)
Other	(84)		(84)
Comprehensive income (loss):
Net income (loss)	83,295					59,540	23,755
Derivative gain (loss), net of reclassifications to earnings and tax	6,183			814			5,369
Adjustments from changes in ownership of Partnership	(703)			(703)
Amortization of terminated interest rate swaps, net of tax	1,009			1,009
Foreign currency translation adjustment	(3,770)			(3,770)
Balance at Jun. 30, 2013	$ 1,752,178	$ 723	$ 3,757,740	$ 21,259	$ (212,874)	$ (1,987,868)	$ 173,198