Derivatives (Derivatives Not Designated as Hedging Instruments - Credit Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative assets - Fair value	$ 834,204	$ 330,316
Derivative liabilities - Fair value	658,515	256,528
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	21,826,497	20,540,031
Derivative assets - Fair value	834,131	330,316
Derivative liabilities - Fair value	657,340	251,744
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives
Derivative [Line Items]
Notional amount	210,357	210,678
Derivative assets - Fair value	8	2
Derivative liabilities - Fair value	218	84
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives \| RPA protection sold
Derivative [Line Items]
Notional amount	199,643	199,964
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	218	84
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives \| RPA protection purchased
Derivative [Line Items]
Notional amount	10,714	10,714
Derivative assets - Fair value	8	2
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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