Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate 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
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	16,657,306	15,489,692
Derivative assets - Fair value	605,122	192,883
Derivative liabilities - Fair value	402,207	124,119
Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	8,340,000	7,750,000
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional amount	897,893	1,003,558
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	179	66
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional amount	518,307	490,852
Derivative assets - Fair value	10,125	1,971
Derivative liabilities - Fair value	2	16
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional amount	6,900,299	6,247,667
Derivative assets - Fair value	593,753	187,294
Derivative liabilities - Fair value	0	6,237
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	8,316,499	7,742,077
Derivative assets - Fair value	603,878	189,265
Derivative liabilities - Fair value	181	6,319
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional amount	897,893	1,003,558
Derivative assets - Fair value	180	67
Derivative liabilities - Fair value	0	0
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Collars and corridors
Derivative [Line Items]
Notional amount	518,307	490,852
Derivative assets - Fair value	2	17
Derivative liabilities - Fair value	10,215	1,996
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional amount	6,924,607	6,253,205
Derivative assets - Fair value	1,062	3,534
Derivative liabilities - Fair value	391,811	115,804
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	8,340,807	7,747,615
Derivative assets - Fair value	1,244	3,618
Derivative liabilities - Fair value	$ 402,026	$ 117,800

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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