Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate Contracts) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative assets - Fair value	$ 242,876	$ 107,816
Derivative liabilities - Fair value	172,923	118,305
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	16,986,784	15,222,341
Derivative assets - Fair value	242,824	107,816
Derivative liabilities - Fair value	169,904	111,828
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	13,469,821	11,695,499
Derivative assets - Fair value	190,388	69,818
Derivative liabilities - Fair value	121,352	69,267
Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,740,000	5,850,000
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional amount	975,369	931,601
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	62	492
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional amount	549,305	429,879
Derivative assets - Fair value	3,277	1,121
Derivative liabilities - Fair value	15	305
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional amount	5,207,158	4,482,881
Derivative assets - Fair value	183,626	41,457
Derivative liabilities - Fair value	4,795	41,545
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,731,832	5,844,361
Derivative assets - Fair value	186,903	42,578
Derivative liabilities - Fair value	4,872	42,342
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional amount	975,369	931,601
Derivative assets - Fair value	64	503
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	549,305	429,879
Derivative assets - Fair value	15	308
Derivative liabilities - Fair value	3,326	1,140
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional amount	5,213,315	4,489,658
Derivative assets - Fair value	3,406	26,429
Derivative liabilities - Fair value	113,154	25,785
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,737,989	5,851,138
Derivative assets - Fair value	3,485	27,240
Derivative liabilities - Fair value	$ 116,480	$ 26,925

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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