Fair Value of Financial Instruments - Summary of Fair Value Information of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Interest and rent receivables, Book value	$ 78,970	$ 57,698
Loans, Book value	1,698,471	986,987
Debt, net Book value	(4,898,667)	(2,909,341)
Interest and rent receivables, Fair value	78,028	57,707
Loans, Fair value	1,722,101	1,017,428
Debt, net Fair value	$ (5,073,707)	$ (2,966,759)