Classification and carrying amount of pledged assets, in which the secured parties are not permitted to sell or repledge the collateral (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total pledged assets	$ 10,803,189	$ 10,496,205
Available For Sale Securities Member
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Assets in which the Secured Parties are Not Permitted to Sell or Repledge the Collateral	1,757,309	1,894,651
Held To Maturity Securities Member
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Assets in which the Secured Parties are Not Permitted to Sell or Repledge the Collateral	25,000	25,000
Loans Held For Sale [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Assets in which the Secured Parties are Not Permitted to Sell or Repledge the Collateral	132	5,286
Loans Held For Investment [Member] \| Covered Loans [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Assets in which the Secured Parties are Not Permitted to Sell or Repledge the Collateral	476,061	0
Loans Held For Investment [Member] \| Non Covered Loans [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged Assets in which the Secured Parties are Not Permitted to Sell or Repledge the Collateral	$ 8,544,687	$ 8,571,268

The carrying amount, as of the date of the latest financial statement presented, of all assets that are pledged as collateral for the payment of the related debt obligation primarily arising from secured borrowings, repurchase agreements or other current or potential obligations, where the secured party does not have the right by contract or custom to sell or re-pledge the collateral and therefore are not reclassified and separately reported in the statement of financial position.

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The sum of the carrying amounts, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of related debt obligations, primarily secured borrowings and repurchase agreements, and for which the transferees are not permitted to sell or re-pledge them to an unrelated party.

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- Definition

The carrying amount as of the date of the latest financial statement presented of other debt securities classified as held to maturity which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

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