Summary of Significant Accounting Policies - Carrying Value and Classification of Related Assets and Maximum Exposure to Loss (Detail)	Sep. 30, 2015 USD ($)
Mortgage and other loans [Member]
Variable Interest Entity [Line Items]
Carrying Amount	$ 922,385,000
Loans, net [Member]
Variable Interest Entity [Line Items]
Maximum Loss Exposure	1,046,215,000
Other assets [Member]
Variable Interest Entity [Line Items]
Carrying Amount	6,297,000
Equity investments [Member]
Variable Interest Entity [Line Items]
Maximum Loss Exposure	$ 54,353,000