EPS Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income	$ 70,395	$ 79,935	$ 153,790	$ 157,995
Dividends declared on preferred stock	(3,750)	(3,750)	(7,500)	(7,500)
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	(472)	(459)	(921)	(890)
Net income to common stockholders - basic and diluted	$ 66,173	$ 75,726	$ 145,369	$ 149,605
Denominator:
Weighted average common shares for basic and diluted earnings per share (in shares)	398,478	386,303	398,398	379,479
Basic and diluted earnings per share (in dollars per share)	$ 0.17	$ 0.20	$ 0.36	$ 0.39
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)			2,300
RSUs
Denominator:
Weighted average grant date fair value (in dollars per share)	$ 6.74		$ 6.74

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period) and after allocation of earnings to participating securities.

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Participating Securities, Distributed and Undistributed Earnings (Loss), Basic and Diluted

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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