Income Taxes - Reconciliation of Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reconciliation of statutory tax to effective tax
Federal statutory tax rate	$ 9,499	$ 47,856
REIT and other non-taxable income	(8,964)	(34,972)
State income taxes	(95)	2,001
Federal benefit of state tax deduction	33	(700)
Valuation allowance		1,255
Other	(379)	511
Effective tax rate	$ 94	$ 15,951
Reconciliation of statutory tax rate to effective tax rate
Federal statutory tax rate (as a percent)	35.00%	35.00%
REIT and other non-taxable income (as a percent)	(33.00%)	(25.60%)
State income taxes (as a percent)	(0.40%)	1.50%
Federal benefit of state tax deduction (as a percent)	0.10%	(0.50%)
Valuation allowance (as a percent)		0.90%
Other (as a percent)	(1.40%)	0.40%
Effective tax rate (as a percent)	0.30%	11.70%