Fair Value Measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 209,697	$ 323,108
Derivatives asset, Fair Value	1,827	15,609
Derivative Liability, Notional Amount	5,505,328	3,268,047
Derivative liability, Fair Value	1,413	14,162
Commodity Contracts [Member] \| Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	4,582,000	2,943,000
Derivative liability, Fair Value	209	249
Other Contracts [Member] \| Foreign Exchange Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	200	400
Derivative liability, Fair Value	1	2
Other Contracts [Member] \| Interest Rate Lock Commitments [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	685	203,648
Derivatives asset, Fair Value	53	9,161
Derivative Liability, Notional Amount		48,638
Derivative liability, Fair Value		923
Other Contracts [Member] \| Forward Start Repurchase Agreement [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Notional Amount	698,000
Derivative liability, Fair Value	0
To Be Announced Security [Member] \| Other Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	202,500	35,650
Derivatives asset, Fair Value	869	4
Derivative Liability, Notional Amount	202,500	24,350
Derivative liability, Fair Value	888	5
Tba Sale Agreements [Member] \| Other Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional		83,810
Derivatives asset, Fair Value		6,444
Derivative Liability, Notional Amount	685	223,846
Derivative liability, Fair Value	39	11,614
Auction Rate Securities Purchase Commitment [Member] \| Other Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	6,512
Derivatives asset, Fair Value	905
Derivative Liability, Notional Amount	21,943	27,813
Derivative liability, Fair Value	$ 276	$ 1,369

Nominal or face amount used to calculate payments on the derivative asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
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-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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+ References

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Nominal or face amount used to calculate payments on the derivative liability.

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