Derivatives (Derivatives Not Designated as Hedging Instruments - Credit Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative assets - Fair value	$ 457,317	$ 602,754
Derivative liabilities - Fair value	344,135	424,828
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional Amount	22,005,910	21,341,158
Derivative assets - Fair value	456,409	602,754
Derivative liabilities - Fair value	342,877	422,729
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives
Derivative [Line Items]
Notional Amount	76,992	76,992
Derivative assets - Fair value	5	13
Derivative liabilities - Fair value	153	206
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives \| RPAs - protection sold
Derivative [Line Items]
Notional Amount	66,278	66,278
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	153	206
Credit contracts \| Derivatives not designated as hedging instruments \| Other credit derivatives \| RPAs - protection purchased
Derivative [Line Items]
Notional Amount	10,714	10,714
Derivative assets - Fair value	5	13
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=121590274&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=121590274&loc=SL5579245-113959

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