Income Taxes - Schedule of Reconciliation of Statutory Income Tax Provisions to the Effective Income Tax Provisions (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Expected tax at statutory rate	$ 71,215	$ 67,012
Non-taxable REIT income	(64,402)	(53,519)
State and local tax expense - net of federal benefit	1,109	615
Change in valuation allowance	1,663	435
Tax Credits (WOTC & Solar)	(2,176)	(4,562)
Miscellaneous	161	3
Total tax expense	$ 7,570	$ 9,984	$ 5,413
Expected tax at statutory rate (as a percent)	35.00%	35.00%
Non-taxable REIT income (as a percent)	(31.70%)	(27.90%)
State and local tax expense - net of federal benefit (as a percent)	0.60%	0.30%
Change in valuation allowance (as a percent)	0.80%	0.20%
Tax credits (WOTC & Solar) (as a percent)	(1.10%)	(2.40%)
Miscellaneous (as a percent)	0.10%	0.00%
Total provision (as a percent)	3.70%	5.20%