Residential Loans at Fair Value - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential Loans Acquired To Be Held For Investment	$ 1,500,000,000	$ 3,000,000,000	$ 594,300,000
Payments to Acquire Charged-off Loans Held for Investment	64,548,000	0	0
Loans and Lease Receivable, Credit Risk	20 days
Residential loans at fair value	11,832,630,000	10,341,375,000
Charged Off Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Purchased, Unpaid Principal Balance	3,500,000,000
Residential loans at fair value	57,217,000	0
Loans Repurchased [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential loans at fair value	$ 3,000,000