Income Taxes - Reconciliation of Statutory Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected tax at statutory rate	$ 144,708	$ 77,151	$ 71,215
Non-taxable REIT income	(131,112)	(67,084)	(64,402)
State and local tax expense - net of federal benefit	2,399	1,249	1,109
Change in valuation allowance	(845)	(624)	1,663
Tax credits/true-up	(312)	274	(2,176)
Miscellaneous	1,009	182	161
Total provision	$ 15,847	$ 11,148	$ 7,570
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Expected tax at statutory rate	35.00%	35.00%	35.00%
Non-taxable REIT income	(31.70%)	(30.40%)	(31.70%)
State and local tax expense - net of federal benefit	0.60%	0.60%	0.60%
Change in valuation allowance	(0.20%)	(0.30%)	0.80%
Tax credits/true-up	(0.10%)	0.10%	(1.10%)
Miscellaneous	0.20%	0.10%	0.10%
Total provision	3.80%	5.10%	3.70%