Equity (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Balance
Total stockholders' equity	$ 3,134,041
Noncontrolling interest	115,743
Total equity	3,249,784	2,855,902
Net loss attributable to noncontrolling interest	(3,528)	(523)
Net income (loss)	(309,445)	56,139
Other comprehensive income	1,179	667
Dividends declared on preferred stocks	(171)	(171)
Dividends declared on common stock	(35,515)	(33,809)
Stock-based compensation	(121)	1,336
Issuance of common stock upon vesting of performance shares, net of shares used for tax withholdings		(5,564)
Excess tax benefit (net tax deficit) on stock-based compensation	(1,632)	4,729
Issuance of common stock	9,864	54,574
Contribution from noncontrolling interest	20,500	16,001
Total stockholders' equity	2,801,728	2,901,588
Noncontrolling interest	132,715	48,216
Total equity	2,934,443	2,949,804
Total stockholders’ equity [Member]
Balance
Total stockholders' equity	3,134,041	2,823,164
Net income (loss) attributable to parent	(305,917)	56,662
Other comprehensive income	1,179	667
Dividends declared on preferred stocks	(171)	(171)
Dividends declared on common stock	(35,515)	(33,809)
Stock-based compensation	(121)	1,336
Issuance of common stock upon vesting of performance shares, net of shares used for tax withholdings		(5,564)
Excess tax benefit (net tax deficit) on stock-based compensation	(1,632)	4,729
Issuance of common stock	9,864	54,574
Contribution from noncontrolling interest	0	0
Total stockholders' equity	2,801,728	2,901,588
Noncontrolling interest [Member]
Balance
Noncontrolling interest	115,743	32,738
Net loss attributable to noncontrolling interest	(3,528)	(523)
Other comprehensive income	0	0
Dividends declared on preferred stocks	0	0
Dividends declared on common stock	0	0
Stock-based compensation	0	0
Issuance of common stock upon vesting of performance shares, net of shares used for tax withholdings		0
Excess tax benefit (net tax deficit) on stock-based compensation	0	0
Issuance of common stock	0	0
Contribution from noncontrolling interest	20,500	16,001
Noncontrolling interest	$ 132,715	$ 48,216