Derivatives (Derivatives Not Designated as Hedging Instruments - Interest Rate Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative assets - Fair value	$ 107,816	$ 67,077
Derivative liabilities - Fair Value	118,305	75,838
Derivative instruments not designated as hedging instruments
Derivative [Line Items]
Notional amount	15,222,341	10,153,108
Derivative assets - Fair value	107,816	67,077
Derivative liabilities - Fair Value	111,828	69,068
Derivative instruments not designated as hedging instruments \| Interest rate contracts
Derivative [Line Items]
Notional amount	11,695,499	9,333,860
Derivative assets - Fair value	69,818	59,564
Derivative liabilities - Fair Value	69,267	58,890
Derivative instruments not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	5,850,000
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Customer Counterparty \| Written options
Derivative [Line Items]
Notional amount	931,601	691,548
Derivative assets - Fair value	0	0
Derivative liabilities - Fair Value	492	223
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Customer Counterparty \| Sold collars and corridors
Derivative [Line Items]
Notional amount	429,879	247,542
Derivative assets - Fair value	1,121	204
Derivative liabilities - Fair Value	305	267
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Customer Counterparty \| Swaps
Derivative [Line Items]
Notional amount	4,482,881	3,724,295
Derivative assets - Fair value	41,457	33,417
Derivative liabilities - Fair Value	41,545	24,636
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Customer Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	5,844,361	4,663,385
Derivative assets - Fair value	42,578	33,621
Derivative liabilities - Fair Value	42,342	25,126
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Financial Counterparty \| Purchased options
Derivative [Line Items]
Notional amount	931,601	691,548
Derivative assets - Fair value	503	233
Derivative liabilities - Fair Value	0	0
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Financial Counterparty \| Collars and corridors
Derivative [Line Items]
Notional amount	429,879	247,542
Derivative assets - Fair value	308	271
Derivative liabilities - Fair Value	1,140	211
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Financial Counterparty \| Swaps
Derivative [Line Items]
Notional amount	4,489,658	3,731,385
Derivative assets - Fair value	26,429	25,439
Derivative liabilities - Fair Value	25,785	33,553
Interest rate contracts \| Derivative instruments not designated as hedging instruments \| Financial Counterparty \| Interest rate contracts
Derivative [Line Items]
Notional amount	5,851,138	4,670,475
Derivative assets - Fair value	27,240	25,943
Derivative liabilities - Fair Value	$ 26,925	$ 33,764

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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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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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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No definition available.

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