Schedule IV - Mortgage Loans on Real Estate (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2015 USD ($)
Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 1,039,765
Face Amount of Loans	9,108,361
Carrying Amount of Loans	9,077,007
Subordinate Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,039,765
Face Amount of Loans	232,845
Carrying Amount of Loans	$ 229,962
Subordinate Loans [Member] \| Various / Diversified [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Various / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates	12.22%
Periodic Payment Terms	I/O
Prior Liens	$ 1,039,765
Face Amount of Loans	232,845
Carrying Amount of Loans	$ 229,962
Senior Mortgage Loans in Excess of 3% of the Carrying Amount of Total Loans [Member] \| MHC [Member] \| Borrower A [Member]
Mortgage Loans on Real Estate [Line Items]
Location	MHC / Diversified-US
Fixed Interest Payment Rates	4.89%
Maximum Maturity Date	2019
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 338,565
Carrying Amount of Loans	$ 339,613
Senior Mortgage Loans in Excess of 3% of the Carrying Amount of Total Loans [Member] \| MHC [Member] \| Borrower B [Member]
Mortgage Loans on Real Estate [Line Items]
Location	MHC / Diversified-US
Fixed Interest Payment Rates	5.29%
Maximum Maturity Date	2016
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 304,710
Carrying Amount of Loans	$ 306,152
Senior Mortgage Loans in Excess of 3% of the Carrying Amount of Total Loans [Member] \| Hotel [Member] \| Borrower C [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Hotel / U.K.
Debt instrument variable rate basis	LIBOR
Interest Payment Rates	4.00%
Maximum Maturity Date	2019
Periodic Payment Terms	I/O
Face Amount of Loans	$ 296,320
Carrying Amount of Loans	$ 293,192
Senior Mortgage Loans in Excess of 3% of the Carrying Amount of Total Loans [Member] \| Office [Member] \| Borrower D [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Office / Northeast
Debt instrument variable rate basis	LIBOR
Interest Payment Rates	3.45%
Maximum Maturity Date	2020
Periodic Payment Terms	I/O
Face Amount of Loans	$ 294,500
Carrying Amount of Loans	$ 292,061
Senior Mortgage Loans in Excess of 3% of the Carrying Amount of Total Loans [Member] \| Office [Member] \| Borrower E [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Office / Northeast
Debt instrument variable rate basis	LIBOR
Interest Payment Rates	3.50%
Maximum Maturity Date	2020
Periodic Payment Terms	I/O
Face Amount of Loans	$ 274,878
Carrying Amount of Loans	272,632
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Face Amount of Loans	7,366,543
Carrying Amount of Loans	$ 7,343,395
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| MHC [Member]
Mortgage Loans on Real Estate [Line Items]
Location	MHC / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	4.67%
Fixed Interest Payment Rates, Maximum	6.30%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 715,857
Carrying Amount of Loans	$ 715,806
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Hotel [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Hotel / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	5.30%
Fixed Interest Payment Rates, Maximum	6.08%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 1,603,592
Carrying Amount of Loans	$ 1,600,332
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Office [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Office / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	4.46%
Fixed Interest Payment Rates, Maximum	6.48%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 3,567,658
Carrying Amount of Loans	$ 3,550,802
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Retail [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Retail / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	5.14%
Fixed Interest Payment Rates, Maximum	5.38%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 610,163
Carrying Amount of Loans	$ 608,275
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Multifamily [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Multifamily / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	4.28%
Fixed Interest Payment Rates, Maximum	6.03%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 542,376
Carrying Amount of Loans	$ 540,184
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Condo / Northeast [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Condo / Northeast
Debt instrument variable rate basis	LIBOR
Interest Payment Rates	3.75%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 84,096
Carrying Amount of Loans	$ 83,920
Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Other [Member]
Mortgage Loans on Real Estate [Line Items]
Location	Other / Diversified
Debt instrument variable rate basis	LIBOR
Fixed Interest Payment Rates, Minimum	4.63%
Fixed Interest Payment Rates, Maximum	6.22%
Periodic Payment Terms	I/O & P/I
Face Amount of Loans	$ 242,801
Carrying Amount of Loans	244,076
Senior Mortgage Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Face Amount of Loans	8,875,516
Carrying Amount of Loans	$ 8,847,045
Minimum [Member] \| Subordinate Loans [Member] \| Various / Diversified [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	10.75%
Maximum Maturity Date	2019
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| MHC [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	1.75%
Maximum Maturity Date	2016
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Hotel [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.25%
Maximum Maturity Date	2016
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Office [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	2.30%
Maximum Maturity Date	2016
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Retail [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.10%
Maximum Maturity Date	2017
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Multifamily [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.40%
Maximum Maturity Date	2017
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Condo / Northeast [Member]
Mortgage Loans on Real Estate [Line Items]
Maximum Maturity Date	2017
Minimum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Other [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	3.30%
Maximum Maturity Date	2016
Maximum [Member] \| Subordinate Loans [Member] \| Various / Diversified [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	12.83%
Maximum Maturity Date	2022
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| MHC [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.00%
Maximum Maturity Date	2021
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Hotel [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.50%
Maximum Maturity Date	2021
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Office [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.50%
Maximum Maturity Date	2020
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Retail [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.50%
Maximum Maturity Date	2019
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Multifamily [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	4.50%
Maximum Maturity Date	2025
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Condo / Northeast [Member]
Mortgage Loans on Real Estate [Line Items]
Maximum Maturity Date	2019
Maximum [Member] \| Senior Mortgage Loans Less Than 3% of the Carrying Amount of Total Loans [Member] \| Other [Member]
Mortgage Loans on Real Estate [Line Items]
Interest Payment Rates	5.00%
Maximum Maturity Date	2019

Stated maturity date of the mortgage loan receivable on real estate, in CCYY format.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum contractual interest rate for funds borrowed, under the debt agreement.

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Minimum contractual interest rate for funds borrowed, under the debt agreement.

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The carrying amount of the outstanding balance due under the mortgage loan.

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Amount of the contractual principal due at the origination of the mortgage loan (face amount).

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Identifies the site (such as country, region, state, county or municipality) of the property or properties under mortgage.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Description of the contractual payment terms of the loan receivable including whether principal and interest is payable at a level or varying amount over the life of the loan, the amount of any balloon payment required at maturity, and any prepayment penalties.

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Amount of prior lien on the real estate that secures the mortgage loan.

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