Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stockholders Equity Note [Line Items]
Declared and paid distributions	$ 211,400,000	$ 487,800,000	$ 137,900,000
Declared and paid distributions (in dollars per share)	$ 0.65	$ 1.5	$ 0.4252
Amounts distributed to stockholders	$ 0	$ 0	$ 0
Stock redeemed (in shares)			1.4
Average price paid per share (in dollars per share)			$ 6.80
Special cash distribution
Stockholders Equity Note [Line Items]
Declared and paid distributions	$ 162,600,000	$ 422,700,000
Declared and paid distributions (in dollars per share)	$ 0.5	$ 1.3