Derivatives (Derivatives Not Designated as Hedging Instruments - Credit Contracts) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative assets - Fair value	$ 242,876	$ 107,816
Derivative liabilities - Fair value	172,923	118,305
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	16,986,784	15,222,341
Derivative assets - Fair value	242,824	107,816
Derivative liabilities - Fair value	169,904	111,828
Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	91,856	119,320
Derivative assets - Fair value	3	1
Derivative liabilities - Fair value	118	164
Credit contracts \| Derivatives not designated as hedging instruments \| Credit contracts
Derivative [Line Items]
Notional amount	91,856	119,320
Derivative assets - Fair value	3	1
Derivative liabilities - Fair value	118	164
Credit contracts \| Derivatives not designated as hedging instruments \| Credit contracts \| RPA protection sold
Derivative [Line Items]
Notional amount	81,142	108,606
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	118	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	3	1
Derivative liabilities - Fair value	$ 0	$ 0

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.

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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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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