Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate 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
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional Amount	17,891,960	18,155,678
Derivative assets - Fair value	319,049	489,132
Derivative liabilities - Fair value	229,032	315,834
Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,960,000	9,090,000
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional Amount	800,962	957,393
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	544	115
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional Amount	531,840	518,477
Derivative assets - Fair value	5,849	7,673
Derivative liabilities - Fair value	158	0
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional Amount	7,597,856	7,586,414
Derivative assets - Fair value	279,361	479,634
Derivative liabilities - Fair value	53,975	1,364
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,930,658	9,062,284
Derivative assets - Fair value	285,210	487,307
Derivative liabilities - Fair value	54,677	1,479
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional Amount	800,962	957,393
Derivative assets - Fair value	551	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	531,840	518,477
Derivative assets - Fair value	160	0
Derivative liabilities - Fair value	5,888	7,717
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional Amount	7,628,500	7,617,524
Derivative assets - Fair value	33,128	1,724
Derivative liabilities - Fair value	168,467	306,623
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional Amount	8,961,302	9,093,394
Derivative assets - Fair value	33,839	1,825
Derivative liabilities - Fair value	$ 174,355	$ 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://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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