Secured Financings - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015 Participants Facility Assets
Debt Instrument [Line Items]
Number of revolving repurchase facilities closed	3
Closing of asset specific repurchase facilities	1
Number of senior loan participation sold	1
Proceeds from line of credit	$ 1,100,000,000
Aggregate borrowings	2,200,000,000
Weighted-average initial maturity	1 year 8 months 12 days
Covenants, minimum tangible net worth	1,100,000,000
Covenants, percentage of tangible assets on cash proceeds from equity issuances	75.00%
Covenants, percentage of recourse indebtedness	5.00%
Maximum [Member]
Debt Instrument [Line Items]
Covenants, EBITDA to fixed charges	1.40%
Covenants, indebtedness to total assets	83.33%
Minimum [Member]
Debt Instrument [Line Items]
Covenants, EBITDA to fixed charges	1.00%
Covenants, minimum cash liquidity amount	10,000,000
Asset-Specific Repurchase Agreements [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance	338,600,000
Revolving Repurchase Facilities [Member]
Debt Instrument [Line Items]
Weighted-average outstanding balance	$ 2,300,000,000
Weighted-Average Cash Coupon [Member]
Debt Instrument [Line Items]
LIBOR basis spread on debt obligation	LIBOR plus 1.87% per annum
LIBOR basis spread on debt obligation	1.87%
Weighted-Average All-in Cost of Credit [Member]
Debt Instrument [Line Items]
LIBOR basis spread on debt obligation	LIBOR plus 2.09% per annum
LIBOR basis spread on debt obligation	2.09%