Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative assets - Fair value	$ 135,782	$ 107,816
Derivative liabilities - Fair value	109,587	118,305
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	15,873,400	15,222,341
Derivative assets - Fair value	135,782	107,816
Derivative liabilities - Fair value	104,909	111,828
Derivatives not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	12,266,761	11,695,499
Derivative assets - Fair value	96,256	69,818
Derivative liabilities - Fair value	71,912	69,267
Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,140,000	5,850,000
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional amount	957,000	931,601
Derivative assets - Fair value	0	0
Derivative liabilities - Fair value	189	492
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional amount	477,225	429,879
Derivative assets - Fair value	1,272	1,121
Derivative liabilities - Fair value	67	305
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional amount	4,695,922	4,482,881
Derivative assets - Fair value	81,642	41,457
Derivative liabilities - Fair value	20,121	41,545
Interest rate contracts \| Derivatives not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,130,147	5,844,361
Derivative assets - Fair value	82,914	42,578
Derivative liabilities - Fair value	20,377	42,342
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional amount	957,000	931,601
Derivative assets - Fair value	193	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	477,225	429,879
Derivative assets - Fair value	67	308
Derivative liabilities - Fair value	1,297	1,140
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional amount	4,702,389	4,489,658
Derivative assets - Fair value	13,082	26,429
Derivative liabilities - Fair value	50,238	25,785
Interest rate contracts \| Derivatives not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	6,136,614	5,851,138
Derivative assets - Fair value	13,342	27,240
Derivative liabilities - Fair value	$ 51,535	$ 26,925

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

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.

+ References

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.

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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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