Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
Dec. 31, 2014
Loss Contingencies [Line Items]
Number of RMBS Trustees Filing Suit	5
Litigation Settlement, Expense	$ 207us-gaap_LitigationSettlementExpense

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

No definition available.

Name:	us-gaap_LitigationSettlementExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration