Real Estate and Loans Receivable - Assets Acquired (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	$ 767,696	$ 654,922	$ 621,490
Land [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	22,569	41,473	518
Building [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	241,242	439,030	8,942
Intangible lease assets - subject to amortization [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	22,513	38,589	1,040
Net investments in direct financing leases [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired		110,580	310,000
Other loans [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	447,664	5,250	95,690
Mortgage loans [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired		20,000	200,000
Other assets [Member]
Significant Acquisitions and Disposals [Line Items]
Total assets acquired	$ 33,708		$ 5,300