EPS Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income	$ 83,011	$ 79,510	$ 240,031	$ 239,754
Dividends declared on preferred stock	(3,750)	(3,750)	(11,250)	(11,250)
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	(442)	(396)	(1,255)	(1,183)
Net income to common stockholders - basic and diluted	$ 78,819	$ 75,364	$ 227,526	$ 227,321
Denominator:
Weighted average common shares for basic and diluted earnings per share (in shares)	373,141,000	372,178,000	373,011,000	372,056,000
Basic and diluted earnings per share (in dollars per share)	$ 0.21	$ 0.20	$ 0.61	$ 0.61
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)			65,280
Weighted average grant date fair value (in dollars per share)	7.24		$ 7.24
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