Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets
Trading securities	$ 141,615	$ 33,172
Available-for-sale securities	1,172,690	1,075,581
MSRs	43,098	5,315
Derivative assets	43,341	2,972
Liabilities
Derivative liabilities	29,571	51,081
Fair Value, Measurements, Recurring
Assets
Trading securities	141,615
Available-for-sale securities	1,172,690
MSRs	43,098
Derivative assets	43,341
Liabilities
Derivative liabilities	29,571
Fair Value, Measurements, Recurring \| Residential Loans at Fair Value
Assets
Loans at fair value	1,219,368
Fair Value, Measurements, Recurring \| Commercial Loans at Fair Value
Assets
Loans at fair value	149,470
Fair Value, Measurements, Recurring \| Level 1
Assets
Derivative assets	8,983
Liabilities
Derivative liabilities	1,786
Fair Value, Measurements, Recurring \| Level 2
Assets
Derivative assets	34,358
Liabilities
Derivative liabilities	27,785
Fair Value, Measurements, Recurring \| Level 2 \| Commercial Loans at Fair Value
Assets
Loans at fair value	149,470
Fair Value, Measurements, Recurring \| Level 3
Assets
Trading securities	141,615
Available-for-sale securities	1,172,690
MSRs	43,098
Fair Value, Measurements, Recurring \| Level 3 \| Residential Loans at Fair Value
Assets
Loans at fair value	$ 1,219,368

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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 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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