EPS Calculation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Numerator:
Net income	$ 78,882		$ 71,328		$ 233,796		$ 224,152
Dividends declared on preferred stock	(3,750)		(3,750)		(11,250)		(10,000)
Dividends, DERs and undistributed earnings allocated to participating securities	(281)		(230)		(842)		(880)
Issuance costs of redeemed preferred stock	0	[1]	0	[1]	0	[1]	(3,947)	[1]
Net income to common stockholders - basic and diluted	$ 74,851		$ 67,348		$ 221,704		$ 209,325
Denominator:
Weighted average common shares for basic and diluted earnings per share	369,690	[2]	363,918	[2]	368,430	[2]	361,181	[2]
Basic and diluted earnings per share (in dollars per share)	$ 0.20		$ 0.19		$ 0.60		$ 0.58
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	1,600				1,600
Restricted common stock
Denominator:
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	358				358
Weighted average grant date fair value (in dollars per share)	$ 7.47				$ 7.47
Restricted Stock Units
Denominator:
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	1,200				1,200
Weighted average grant date fair value (in dollars per share)	$ 6.83				$ 6.83

[1] Issuance costs of redeemed preferred stock represent the original offering costs related to the Series A Preferred Stock, which was redeemed on May 16, 2013. (See Note 11)

[2] At September 30, 2014, the Company had an aggregate of 1.6 million equity instruments outstanding that were not included in the calculation of diluted EPS for the three and nine months ended September 30, 2014, as their inclusion would have been anti-dilutive. These equity instruments were comprised of approximately 358,000 shares of restricted common stock with a weighted average grant date fair value of $7.47 and approximately 1.2 million RSUs with a weighted average grant date fair value of $6.83. These equity instruments may have a dilutive impact on future EPS.