Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Trading securities	$ 111,606us-gaap_TradingSecurities	$ 124,555us-gaap_TradingSecurities
Available-for-sale securities	1,267,624us-gaap_AvailableForSaleSecurities	1,558,306us-gaap_AvailableForSaleSecurities
Derivative assets	16,417us-gaap_DerivativeAssets	7,787us-gaap_DerivativeAssets
MSRs	139,293us-gaap_ServicingAssetAtFairValueAmount	64,824us-gaap_ServicingAssetAtFairValueAmount	5,315us-gaap_ServicingAssetAtFairValueAmount
Pledged collateral	9,927
Liabilities
Derivative liabilities	58,331us-gaap_DerivativeLiabilities	18,167us-gaap_DerivativeLiabilities
Commercial secured borrowings	66,707us-gaap_LongTermDebtFairValue	66,146us-gaap_LongTermDebtFairValue
Fair Value, Measurements, Recurring
Assets
Trading securities	111,606	124,555
Available-for-sale securities	1,267,624	1,558,306
Derivative assets	16,417	7,787
MSRs	139,293	64,824
Pledged collateral	9,927
FHLBC stock	10,688
Guarantee asset	7,201
Liabilities
Derivative liabilities	58,331	18,167
Commercial secured borrowings	66,707
Fair Value, Measurements, Recurring \| Residential Loans at Fair Value
Assets
Loans at fair value	1,922,700	402,602
Fair Value, Measurements, Recurring \| Commercial Loans at Fair Value
Assets
Loans at fair value	237,496	89,111
Fair Value, Measurements, Recurring \| Level 1
Assets
Derivative assets	6,654	1,139
Pledged collateral	9,927
FHLBC stock	10,688
Liabilities
Derivative liabilities	9,878	1,189
Fair Value, Measurements, Recurring \| Level 2
Assets
Derivative assets	8,603	6,648
Liabilities
Derivative liabilities	48,412	16,599
Fair Value, Measurements, Recurring \| Level 2 \| Residential Loans at Fair Value
Assets
Loans at fair value	244,716	11,502
Fair Value, Measurements, Recurring \| Level 3
Assets
Trading securities	111,606	124,555
Available-for-sale securities	1,267,624	1,558,306
Derivative assets	1,160
MSRs	139,293	64,824
Guarantee asset	7,201
Liabilities
Derivative liabilities	41	379
Commercial secured borrowings	66,707
Fair Value, Measurements, Recurring \| Level 3 \| Residential Loans at Fair Value
Assets
Loans at fair value	1,677,984	391,100
Fair Value, Measurements, Recurring \| Level 3 \| Commercial Loans at Fair Value
Assets
Loans at fair value	$ 237,496	$ 89,111

Guarantees, Asset, Fair Value

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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- Definition

Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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No definition available.

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The fair value, as of the date of each statement of financial position presented, of other assets which are owned but transferred to serve as collateral for the payment of the related debt obligation, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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Fair value portion of receivables, including, but not limited to, trade account receivables, note receivables, and loan receivables.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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-Glossary Trading Securities

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