Fair Value of Financial Instruments Measured at Fair Value - Quantitative Information about Significant Unobservable Inputs Used for Fair Value Measurements (Detail)	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Fair Value Inputs [Abstract]
Cumulative prepayment rates	21.50%us-gaap_FairValueInputsPrepaymentRate	20.00%us-gaap_FairValueInputsPrepaymentRate
Market servicing rates (% per annum on unpaid principal balance)	0.50%	0.50%
Minimum
Fair Value Inputs [Abstract]
Market servicing rates (% per annum on unpaid principal balance)	0.40%
Maximum
Fair Value Inputs [Abstract]
Market servicing rates (% per annum on unpaid principal balance)	0.70%
Level 3 Inputs \| Minimum \| Loans, notes and certificates
Fair Value Inputs [Abstract]
Discount rates	5.10%	5.20%
Net cumulative expected loss rates	0.30%	0.30%
Level 3 Inputs \| Minimum \| Servicing asset/liability
Fair Value Inputs [Abstract]
Discount rates	3.50%	5.30%
Net cumulative expected loss rates	0.30%	0.30%
Cumulative prepayment rates	16.40%	16.50%
Market servicing rates (% per annum on unpaid principal balance)	0.50%	0.50%
Level 3 Inputs \| Maximum \| Loans, notes and certificates
Fair Value Inputs [Abstract]
Discount rates	17.20%	17.40%
Net cumulative expected loss rates	22.20%	22.00%
Level 3 Inputs \| Maximum \| Servicing asset/liability
Fair Value Inputs [Abstract]
Discount rates	23.40%	23.70%
Net cumulative expected loss rates	22.20%	22.00%
Cumulative prepayment rates	36.00%	26.70%
Market servicing rates (% per annum on unpaid principal balance)	0.70%	0.70%
Level 3 Inputs \| Weighted- Average \| Loans, notes and certificates
Fair Value Inputs [Abstract]
Discount rates	10.00%	10.10%
Net cumulative expected loss rates	10.20%	10.00%
Level 3 Inputs \| Weighted- Average \| Servicing asset/liability
Fair Value Inputs [Abstract]
Discount rates	10.40%	10.70%
Net cumulative expected loss rates	10.20%	10.20%
Cumulative prepayment rates	21.50%	20.00%
Market servicing rates (% per annum on unpaid principal balance)	0.50%	0.50%

Fair Value Inputs Market Servicing Rate

No definition available.

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- Details

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

+ Details

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- Definition

Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value.

+ References

+ Details

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