Fair Value Measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 323,207	$ 440,884
Derivatives asset, Fair Value	11,152	12,111
Derivative liability, notional	2,867,046	5,011,304
Derivative liability, Fair Value	8,700	3,505
Other Contracts [Member] | Interest Rate Lock Commitments [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	265,717	147,521
Derivatives asset, Fair Value	10,808	7,576
Derivative liability, notional	4,714	22,269
Derivative liability, Fair Value	187	1,222
Other Contracts [Member] | Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	600	400,000
Other Contracts [Member] | To Be Announced Security [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	57,490	105,185
Derivatives asset, Fair Value	344	1,026
Derivative liability, notional	54,140	105,186
Derivative liability, Fair Value	321	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		188,178
Derivatives asset, Fair Value		3,509
Derivative liability, notional	301,991
Derivative liability, Fair Value	6,840
Other Contracts [Member] | Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, Fair Value	5	10
Other Contracts [Member] | Auction Rate Securities Purchase Commitment [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	9,601	12,249
Derivative liability, Fair Value	477	902
Commodity Contracts [Member] | Future [Member]
Derivatives, Fair Value [Line Items]
Derivative liability, notional	2,496,000	3,835,600
Derivative liability, Fair Value	$ 870	$ 353