Derivatives (Derivatives Not Designated as Hedging Instruments - Credit Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative assets - Fair value	$ 135,782	$ 107,816
Derivative liabilities - Fair value	109,587	118,305
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	15,873,400	15,222,341
Derivative assets - Fair value	135,782	107,816
Derivative liabilities - Fair value	104,909	111,828
Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	92,925	119,320
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	81	164
Credit contracts \| Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	92,925	119,320
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	81	164
Credit contracts \| Derivatives not designated as hedging instruments \| Credit contracts \| RPA protection sold
Derivative [Line Items]
Notional amount	82,211	108,606
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	81	164
Credit contracts \| Derivatives not designated as hedging instruments \| Credit contracts \| RPA protection purchased
Derivative [Line Items]
Notional amount	10,714	10,714
Derivative assets - Fair value	1	1
Derivative liabilities - Fair value	$ 0	$ 0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and elected not to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and elected not to be offset.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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