Fair Value Measurements (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Fair Value Measurements
Aggregate fair value of PrimeLending's mortgage loans held for sale accounted for under the Fair Value Option	1,270,000,000	$ 1,060,000,000
Unpaid principal balance of PrimeLending loans held for sale accounted under the fair value option	1,220,000,000	1,040,000,000
Financial assets and liabilities
Trading securities	65,717,000us-gaap_TradingSecurities	58,846,000us-gaap_TradingSecurities
Available for sale securities	925,535,000us-gaap_AvailableForSaleSecurities	1,203,143,000us-gaap_AvailableForSaleSecurities
Mortgage servicing asset	36,155,000us-gaap_ServicingAssetAtFairValueAmount	20,149,000us-gaap_ServicingAssetAtFairValueAmount
Maximum
Fair value measurements
Holding period of mortgage loans held for sale	30 days
Level 2
Financial assets and liabilities
Loans held for sale	37,541,000	29,322,000
Time deposits	6,365,555,000	6,722,909,000
Estimate of Fair Value Measurement
Financial assets and liabilities
Loans held for sale	37,541,000	29,322,000
Time deposits	6,365,555,000	6,722,909,000
Recurring \| Level 1
Financial assets and liabilities
Trading securities	39,000	33,000
Available for sale securities	13,762,000	22,079,000
Investment in SWS common stock	70,282,000
Recurring \| Level 2
Financial assets and liabilities
Trading securities	65,678,000	58,813,000
Available for sale securities	911,773,000	1,121,011,000
Loans held for sale	1,263,135,000	1,031,988,000
Derivative assets	23,805,000	23,564,000
Trading liabilities	48,000	46,000
Derivative liabilities	12,849,000	139,000
Recurring \| Level 3
Financial assets and liabilities
Available for sale securities		60,053,000
Loans held for sale	9,017,000	27,729,000
Mortgage servicing asset	36,155,000	20,149,000
Derivative liabilities		5,600,000
Recurring \| Estimate of Fair Value Measurement
Financial assets and liabilities
Trading securities	65,717,000	58,846,000
Available for sale securities	925,535,000	1,203,143,000
Loans held for sale	1,272,152,000	1,059,717,000
Derivative assets	23,805,000	23,564,000
Mortgage servicing asset	36,155,000	20,149,000
Investment in SWS common stock	70,282,000
Trading liabilities	48,000	46,000
Derivative liabilities	12,849,000	$ 5,739,000

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Represents the aggregate fair value of loans held for sale accounted for under the fair value option.

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Represents the amount of unpaid principal balance of loans held for sale accounted under the fair value option.

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Represents the period of time a loan held-for-sale is reported on the balance sheet.

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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 portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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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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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance 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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Fair value portion of liabilities pertaining to principal and customer trading transactions, or which may be incurred with the objective of generating a profit from short-term fluctuations in price as part of an entity's market-making, hedging and proprietary trading. Examples include, but are not limited to, short positions in securities, derivatives and commodities.

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