EPS Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 78,950	$ 78,071	$ 157,020	$ 160,244
Dividends declared on preferred stock	(3,750)	(3,750)	(7,500)	(7,500)
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	(421)	(391)	(814)	(786)
Net income to common stockholders - basic and diluted	$ 74,779	$ 73,930	$ 148,706	$ 151,958
Denominator:
Weighted average common shares for basic and diluted earnings per share (in shares)	373,023,000	370,164,000	372,946,000	371,992,000
Basic and diluted earnings per share (in dollars per share)	$ 0.20	$ 0.20	$ 0.40	$ 0.41
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)			2,100,000
Restricted shares of common stock
Denominator:
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)			80,429
Weighted average grant date fair value (in dollars per share)	7.32		$ 7.32
RSUs
Denominator:
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)			2,100,000
Weighted average grant date fair value (in dollars per share)	$ 6.84		$ 6.84