Note to Schedule IV - Reconciliation of Mortgage Loans on Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Mortgage Loans On Real Estate [Abstract]
Balance at beginning of period	$ 969,172	$ 0
Additions during period:
New loans	0	1,018,120
Premium on new loans	0	12,437
Deductions during period:
Collections of principal	(221,615)	(59,717)
Amortization of premium	(3,095)	(1,465)
Provision for loan losses	0	(203)
Balance at end of period	$ 744,462	$ 969,172