Fair Value Measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 613,276	$ 440,884
Derivatives asset, Fair Value	7,646	12,111
Derivative liability, notional	3,517,933	5,011,304
Derivative liability, Fair Value	2,614	3,505
Other Contracts [Member] | Interest Rate Lock Commitments [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	219,603	147,521
Derivatives asset, Fair Value	5,060	7,576
Derivative liability, notional	46,598	22,269
Derivative liability, Fair Value	683	1,222
Other Contracts [Member] | Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	400	400,000
Other Contracts [Member] | To Be Announced Security [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	55,725	105,185
Derivatives asset, Fair Value	183	1,026
Derivative liability, notional	51,275	105,186
Derivative liability, Fair Value	171	1,018
Other Contracts [Member] | Forward Start Repurchase Agreement [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional		636,000
Derivative liability, Fair Value		0
Other Contracts [Member] | Tba Sale Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	337,948	188,178
Derivatives asset, Fair Value	2,403	3,509
Other Contracts [Member] | Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair Value	28	10
Other Contracts [Member] | Auction Rate Securities Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	16,660	12,249
Derivative liability, Fair Value	1,034	902
Commodity Contracts [Member] | Future [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	3,403,000	3,835,600
Derivative liability, Fair Value	$ 698	$ 353