EPS Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income	$ 83,395	$ 78,060
Dividends declared on preferred stock	(3,750)	(3,750)
Dividends, dividend equivalents and undistributed earnings allocated to participating securities	(449)	(431)
Net income to common stockholders - basic and diluted	$ 79,196	$ 73,879
Denominator:
Weighted average common shares for basic and diluted earnings per share (in shares)	398,317	372,579
Basic and diluted earnings per share (in dollars per share)	$ 0.20	$ 0.20
Anti-dilutive securities excluded from diluted earnings per share calculations (in shares)	2,200
RSUs
Denominator:
Weighted average grant date fair value (in dollars per share)	$ 6.90

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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 portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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