Real Estate and Loans Receivable - Assets Acquired (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Equity investments and other assets	$ 70,166	$ 101,716	$ 33,708
Liabilities assumed	(6,319)	(317)
Total assets acquired	1,682,409	2,218,869	767,696
Loans repaid	(193,262)	(385,851)
Total net assets acquired	1,489,147	1,833,018	767,696
Land [Member]
Business Acquisition [Line Items]
Total assets acquired	91,176	120,746	22,569
Building [Member]
Business Acquisition [Line Items]
Total assets acquired	654,772	741,935	241,242
Intangible Lease Assets - Subject to Amortization [Member]
Business Acquisition [Line Items]
Total assets acquired	94,614	176,383	22,513
Net Investments in Direct Financing Leases [Member]
Business Acquisition [Line Items]
Total assets acquired	178,000	174,801
Other Loans [Member]
Business Acquisition [Line Items]
Total assets acquired		523,605	$ 447,664
Mortgage Loans [Member]
Business Acquisition [Line Items]
Total assets acquired	$ 600,000	$ 380,000