Loan Participations Sold - Summary of Statistics for Loan Participations Sold (Parenthetical) (Detail) $ in Thousands, £ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 GBP (£)	Dec. 31, 2015 USD ($)
Participating Mortgage Loans [Line Items]
Guarantor obligations	$ 32,200		$ 32,200		£ 24.0
Interest paid			84,408	$ 43,558
Deferred financing costs	16,789		16,789			$ 15,646
Loan Participations Sold [Member]
Participating Mortgage Loans [Line Items]
Interest expense	3,700	$ 4,900	7,400	9,200
Interest paid	3,600	$ 4,700	7,100	$ 8,700
Deferred financing costs	$ 1,900		$ 1,900			$ 2,000