Real Estate and Lending Activities - Assets Acquired (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Total assets acquired	$ 1,166,618	$ 2,152,069
Equity investments	245,267	100,000
Liabilities assumed		(878)
Loans repaid	(525,426)
Total net assets acquired	641,192	2,152,069
Other Loans [Member]
Business Acquisition [Line Items]
Total assets acquired	336,458
Mortgage Loans [Member]
Business Acquisition [Line Items]
Total assets acquired		700,000
Land and Land Improvements [Member]
Business Acquisition [Line Items]
Total assets acquired	57,452	220,864
Building [Member]
Business Acquisition [Line Items]
Total assets acquired	467,164	928,687
Intangible Lease Assets - Subject to Amortization [Member]
Business Acquisition [Line Items]
Total assets acquired	$ 60,277	162,946
Net Investments in Direct Financing Leases [Member]
Business Acquisition [Line Items]
Total assets acquired		$ 40,450