Commercial Real Estate Investments - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Real Estate Properties [Line Items]
Transaction costs related to acquisitions			$ 7,300,000
Securitization financing transaction, purchase	399,500,000	1,554,958,000	1,583,969,000
Securitization financing transaction, total	260,700,000	260,700,000
Securitization financing transaction, weighted average rate	65.30%
Securitization financing transaction, variable interest rate	1.74%
Securitization financing transaction, variable interest rate description		LIBOR plus 1.74% at closing
General and Administrative Expense
Real Estate Properties [Line Items]
Transaction costs related to acquisitions		1,000,000
Other Assets
Real Estate Properties [Line Items]
Securitization cost	$ 4,300,000