Stockholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended			3 Months Ended								5 Months Ended	12 Months Ended
	Dec. 21, 2012	Aug. 23, 2012	Aug. 06, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	May 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 23, 2012
Equity [Abstract]
Cash Dividend on Common Stock				$ 0.55	$ 0.55	$ 0.55	$ 0.55	$ 0.50	$ 0.50	$ 0.50	$ 0.50		$ 2.20	$ 2.00	$ 6.84
Aggregated Dividend Paid													$ 112,000,000	$ 101,700,000
Issuance of common stock	6.7
Distribution of common stock	62,000,000												109,414,000	76,424,000	62,007,000
Minimum percentage of adjusted funds from operations as cash dividend													50.00%
Percentage of REIT taxable income as cash dividend													100.00%
Required distribution , REIT taxable income													90.00%
Repurchase agreement, Total cost			185,400,000									100,000,000		100,028,000	185,400,000
Company repurchased, shares			5.0									2.3
Authorized amount for share repurchase program															100,000,000
Common stock offered and sold		0.8
Sale of common stock, price per share																$ 40.00
Issuance of common stock		$ 32,700,000													$ 32,722,000