Schedule IV - Reconciliation of Mortgage Loans on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Mortgage Loans on Real Estate [Abstract]
Balance at January 1,	$ 9,077,007	$ 4,428,500	$ 2,047,223
Additions during period:
Loan fundings	3,151,882	7,203,145	3,067,263
Amortization of deferred fees and expenses	40,345	36,052	19,785
Deductions during period:
Collections of principal	(3,351,042)	(2,407,920)	(564,183)
Unrealized loss on foreign currency translation	(156,937)	(149,269)	(52,076)
Deferred origination fees and expenses	(44,697)	(33,501)	(35,449)
Loans sold	(23,580)		(27,063)
Transfers to other assets			(27,000)
Balance at December 31,	$ 8,692,978	$ 9,077,007	$ 4,428,500