Fair Value of Financial Instruments - Equity Interest in Related Party and Related Loans Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	$ 920,901	$ 200,750
Cost	920,901	200,750
Fair Value Measurements, Recurring [Member] | Equity investments [Member] | Other Assets [Member]
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	7,349	3,300
Cost	7,349	3,300
Fair Value Measurements, Recurring [Member] | Acquisition loans [Member] | Other Loans [Member]
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	603,552	97,450
Cost	603,552	97,450
Fair Value Measurements, Recurring [Member] | Mortgage Loans [Member] | Mortgage loans [Member]
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	310,000	100,000
Cost	$ 310,000	$ 100,000