Capital Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 18, 2013
Class Of Stock [Line Items]
Number of authorized preferred stock	25,000,000	25,000,000
7.625% Series A Cumulative Redeemable Preferred stock, par value	$ 0.001	$ 0.001
Series A preferred stock dividend rate per year	7.625%	7.625%
Total liquidation preference value	$ 287,500	$ 287,500
Common stock share authorized to repurchase	6,345,153
Common stock shares authorized to repurchase					10,000,000
Stock repurchased during period, shares	1,443,283	100,000
Stock repurchased during period, value	$ 20,753	$ 1,912	$ 43,881
7.625% Series A Cumulative Redeemable Preferred Stock
Class Of Stock [Line Items]
7.625% Series A Cumulative Redeemable Preferred stock, par value				$ 0.001
Issuance of Common stock, shares				11,500,000
Shares issued pursuant to full exercise of underwriters' over allotment option				1,500,000
Liquidation preference per share				$ 25.00
Series A preferred stock dividend rate per year				7.625%
Annual dividend per share on the preferred stock				$ 1.90625
Total liquidation preference value				$ 287,500
Series A preferred stock, redemption date				Aug. 27, 2017