Fair Value of Financial Instruments - Equity Interest in Related Party and Related Loans Measured at Fair Value on Recurring Basis (Detail) $ in Thousands	Mar. 31, 2018 USD ($)
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	$ 227,256
Original Cost	233,010
Fair Value Measurements, Recurring [Member] | Equity Method Investments and Other Loans [Member] | Other Loans and Other Assets [Member]
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	112,256
Original Cost	118,010
Fair Value Measurements, Recurring [Member] | Mortgage Loans [Member] | Mortgage Loans [Member]
Financial Instruments Measured At Fair Value On Recurring Basis [Line Items]
Fair Value	115,000
Original Cost	$ 115,000