Fair Value Measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) (Not Designated as Hedging Instrument, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 440,884	[1]	$ 407,246	[1]
Derivatives asset, Fair Value	12,111	[1]	4,530	[1]
Derivative liability, notional	5,011,304	[1]	7,188,207	[1]
Derivative liability, Fair Value	3,505	[1]	6,574	[1]
Other Contracts | TBA
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	105,185	[1]	25,262	[1]
Derivatives asset, Fair Value	1,026	[1]	134	[1]
Derivative liability, notional	105,186	[1]	14,547	[1]
Derivative liability, Fair Value	1,018	[1]	73	[1]
Other Contracts | TBA Sale Agreements
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	188,178	[1]	266,415	[1]
Derivatives asset, Fair Value	3,509	[1]	2,021	[1]
Other Contracts | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Derivative liability, notional	400,000	[1]
Derivative liability, Fair Value	10	[1]
Other Contracts | Forward Start Repurchase Agreement
Derivatives, Fair Value [Line Items]
Derivative liability, notional	636,000	[1]	506,000	[1]
Derivative liability, Fair Value	0	[1]	0	[1]
Other Contracts | Auction Rate Securities Purchase Commitment
Derivatives, Fair Value [Line Items]
Derivative liability, notional	12,249	[1]	29,056	[1]
Derivative liability, Fair Value	902	[1]	2,600	[1]
Other Contracts | Interest rate lock commitments
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	147,521	[1]	115,569	[1]
Derivatives asset, Fair Value	7,576	[1]	2,375	[1]
Derivative liability, notional	22,269	[1]	76,604	[1]
Derivative liability, Fair Value	1,222	[1]	3,653	[1]
Commodity Contracts | U.S. treasury futures
Derivatives, Fair Value [Line Items]
Derivative liability, notional	102,600	[1],[2]	60,000	[1],[3]
Derivative liability, Fair Value	252	[1],[2]	186	[1],[3]
Commodity Contracts | Federal funds futures
Derivatives, Fair Value [Line Items]
Derivative liability, notional	3,260,000	[1],[2]	6,155,000	[1],[3]
Derivative liability, Fair Value	43	[1],[2]	18	[1],[3]
Commodity Contracts | Euro Dollars Futures
Derivatives, Fair Value [Line Items]
Derivative liability, notional	333,000	[1],[2]	347,000	[1],[3]
Derivative liability, Fair Value	55	[1],[2]	44	[1],[3]
Commodity Contracts | General collateral futures
Derivatives, Fair Value [Line Items]
Derivative liability, notional	140,000	[1],[2]
Derivative liability, Fair Value	$ 3	[1],[2]

[1] See “Derivative Instruments and Hedging Activities” above for description of derivative financial instruments. Such derivative instruments are not subject to master netting agreements, thus the related amounts are not offset.

[2] Included in payable to brokers, dealers and clearing organizations on the consolidated balance sheet.

[3] For the year ended December 31, 2014, the diluted earnings per share computation does not include the anti-dilutive effect of 43,008 shares of Class A Stock granted under share-based compensation arrangements (57,573 and 1,936,871 shares of Class A Stock granted under share-based compensation arrangements together with the warrant described in (1) for the years ended December 31, 2013 and 2012, respectively).