Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate Contracts) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative assets - Fair value	$ 588,582	$ 602,754
Derivative liabilities - Fair value	448,921	424,828
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional Amount	21,676,672	21,341,158
Derivative assets - Fair value	588,582	602,754
Derivative liabilities - Fair value	447,542	422,729
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional Amount	17,836,695	18,155,678
Derivative assets - Fair value	329,953	489,132
Derivative liabilities - Fair value	227,768	315,834
Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,930,000	9,090,000
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional Amount	850,152	957,393
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	650	115
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional Amount	424,212	518,477
Derivative assets - Fair value	3,864	7,673
Derivative liabilities - Fair value	218	0
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional Amount	7,628,895	7,586,414
Derivative assets - Fair value	309,520	479,634
Derivative liabilities - Fair value	25,743	1,364
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,903,259	9,062,284
Derivative assets - Fair value	313,384	487,307
Derivative liabilities - Fair value	26,611	1,479
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional Amount	850,152	957,393
Derivative assets - Fair value	656	101
Derivative liabilities - Fair value	0	15
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Collars and corridors
Derivative [Line Items]
Notional Amount	424,212	518,477
Derivative assets - Fair value	214	0
Derivative liabilities - Fair value	3,910	7,717
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional Amount	7,659,072	7,617,524
Derivative assets - Fair value	15,699	1,724
Derivative liabilities - Fair value	197,247	306,623
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,933,436	9,093,394
Derivative assets - Fair value	16,569	1,825
Derivative liabilities - Fair value	$ 201,157	$ 314,355

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://www.xbrl.org/2003/role/disclosureRef
-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

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313

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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=125515794&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=125515794&loc=SL5579245-113959

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