Net Income per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income	$ 36,235	$ 10,338	$ 83,359	$ 28,956
Preferred dividends	(9,310)	(5,860)	(18,620)	(11,675)
Net income available to common stockholders	26,925	4,478	64,739	17,281
Dividends declared on common stock	(48,501)	(31,005)	(90,647)	(62,002)
Dividends on participating securities	(630)	(437)	(1,259)	(885)
Net (loss) attributable to common stockholders	$ (22,206)	$ (26,964)	$ (27,167)	$ (45,606)
Denominator:
Basic weighted average shares of common stock outstanding (shares)	95,428,134	67,402,311	93,530,831	67,393,751
Diluted weighted average shares of common stock outstanding (shares)	96,796,289	68,374,557	94,907,762	68,351,137
Basic and diluted net income per weighted average share of common stock
Distributable Earnings (in dollars per share)	$ 0.51	$ 0.46	$ 0.97	$ 0.92
Undistributed (loss) (in dollars per share)	(0.23)	(0.40)	(0.29)	(0.68)
Basic and diluted net income per share of common stock (in dollars per share)	$ 0.28	$ 0.06	$ 0.68	$ 0.24
RSUs [Member]
Basic and diluted net income per weighted average share of common stock
Unvested securities excluded from earnings per share calculation	1,368,155	972,246	1,376,930	957,386

Earnings Per Share, Basic and Diluted, Distributed

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Earnings Per Share, Basic and Diluted, Undistributed

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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 cash, stock, and paid-in-kind (PIK) dividends declared, for example, but not limited to, common and preferred stock.

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

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