Financial Instruments - Notional Amounts and Fair Values of Derivatives by Product (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 454,308	$ 407,246
Derivatives asset, Fair Value	12,422	4,530
Derivative liability, notional	4,663,806	7,188,207
Derivative liability, Fair Value	5,847	6,574
Commodity Contracts [Member] | U.S. Treasury Futures [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	80,000	60,000
Derivative liability, Fair Value	188	186
Commodity Contracts [Member] | Federal Funds Futures [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	4,195,000	6,155,000
Derivative liability, Fair Value	43	18
Commodity Contracts [Member] | Euro Dollars Futures [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	285,000	347,000
Derivative liability, Fair Value	88	44
Other Contracts [Member] | Interest Rate Lock Commitments [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	170,715	115,569
Derivatives asset, Fair Value	10,528	2,375
Derivative liability, notional	49,182	76,604
Derivative liability, Fair Value	3,833	3,653
Other Contracts [Member] | Tba [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	44,515	25,262
Derivatives asset, Fair Value	144	134
Derivative liability, notional	34,412	14,547
Derivative liability, Fair Value	181	73
Other Contracts [Member] | Tba Sale Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	239,078	266,415
Derivatives asset, Fair Value	1,750	2,021
Other Contracts [Member] | Forward Start Repurchase Agreement [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional		506,000
Other Contracts [Member] | Auction Rate Securities Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	20,212	29,056
Derivative liability, Fair Value	$ 1,514	$ 2,600