Income Taxes - Additional Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Tax Credit Carryforward [Line Items]
Aggregate tax basis of stockholders' equity in excess of assets and liabilities	$ (333,763)
Aggregate tax basis of stockholders' equity in excess of assets and liabilities (dollars per share)	$ (9.10)
Common stock, shares issued (in shares)	36,692		36,682
Payment of dividends	$ 40,298	$ 46,391
Estimated REIT Taxable Income	$ 21,091	$ 33,521
Capital Loss Carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward			$ (5,175)	$ (341,850)	$ (579,322)