Financial Derivatives - Schedule of Derivative Instruments in Statement of Financial Position (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Notional Disclosures [Abstract]
Notional Amount	$ 13,799,053		$ 9,955,745
Fair Value
Asset	5,589		7,487
Collateral (held)/pledged	(2,655)		(1,778)
Net amount	2,934		5,709
(Liability)	(30,542)		(19,633)
Collateral (held)/pledged	167,060		47,018
Net amount	136,518		27,385
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Swap, Pay Fixed Non-Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	4,913,988		3,097,084
Fair Value
Asset	2,448		3,004
(Liability)	$ (4,942)		$ (4,326)
Weighted- Average Pay Rate	2.47%		2.42%
Weighted- Average Receive Rate	2.18%		2.58%
Weighted- Average Remaining Term (in years)	11 years 3 months 18 days	9 years 9 months
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Swap, Receive Fixed Non-Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 1,547,200		$ 1,871,200
Fair Value
Asset	266		547
(Liability)	$ (5,004)		$ (4,484)
Weighted- Average Pay Rate	2.17%		2.50%
Weighted- Average Receive Rate	2.08%		1.84%
Weighted- Average Remaining Term (in years)	1 year 4 months 17 days	1 year 6 months 29 days
Designated as Hedging Instrument [Member] \| Fair Value Hedging [Member] \| Interest Rate Swap, Receive Fixed Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 340,000		$ 160,000
Fair Value
Asset	891		338
(Liability)	$ (178)		$ (28)
Weighted- Average Pay Rate	2.09%		2.35%
Weighted- Average Receive Rate	2.58%		3.06%
Weighted- Average Remaining Term (in years)	2 years 3 months 29 days	2 years 10 months 28 days
Designated as Hedging Instrument [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap, Pay Fixed Non-Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 428,000		$ 373,000
Fair Value
Asset	1,338		2,441
(Liability)	$ (2,989)		$ (99)
Weighted- Average Pay Rate	2.36%		2.40%
Weighted- Average Receive Rate	2.41%		2.83%
Weighted- Average Remaining Term (in years)	5 years 8 months 4 days	6 years 1 month 13 days
Not Designated as Hedging Instrument [Member]
Fair Value
Credit valuation adjustment	$ 0		$ (60)
Credit valuation adjustment	55		21
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap, Pay Fixed Non-Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	329,745		316,664
Fair Value
Asset	0		796
(Liability)	$ (16,899)		$ (10,399)
Weighted- Average Pay Rate	3.59%		3.69%
Weighted- Average Receive Rate	2.26%		2.52%
Weighted- Average Remaining Term (in years)	5 years 7 months 24 days	6 years 3 months
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap, Receive Fixed Non-Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 2,785,020		$ 2,347,371
Fair Value
Asset	0		0
(Liability)	$ 0		$ 0
Weighted- Average Pay Rate	2.10%		2.37%
Weighted- Average Receive Rate	2.19%		2.10%
Weighted- Average Remaining Term (in years)	1 year 4 months 24 days	10 months 9 days
Not Designated as Hedging Instrument [Member] \| Interest Rate Swap, Receive Fixed Callable [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 655,000
Fair Value
Asset	180
(Liability)	$ (17)
Weighted- Average Pay Rate	1.48%
Weighted- Average Receive Rate	1.64%
Weighted- Average Remaining Term (in years)	9 months 3 days
Not Designated as Hedging Instrument [Member] \| Basis Swap [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 2,770,500		$ 1,770,026
Fair Value
Asset	466		421
(Liability)	$ (543)		$ (130)
Weighted- Average Pay Rate	2.07%		2.45%
Weighted- Average Receive Rate	2.01%		2.49%
Weighted- Average Remaining Term (in years)	11 months 12 days	1 year 3 months 7 days
Not Designated as Hedging Instrument [Member] \| Future [Member]
Notional Disclosures [Abstract]
Notional Amount	$ 29,600		$ 20,400
Fair Value
Asset			0
(Liability)	$ (25)		$ (188)
Weighted- Average Forward Price (in dollars per share)	$ 130.23	$ 121.09

Derivative, Weighted-Average Forward Price

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Fair value of securities received as collateral against derivative assets.

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Nominal or face amount used to calculate payments on the derivative asset.

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- Definition

Average fixed interest rate related to the group of interest rate derivatives.

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Average variable interest rate related to the group of interest rate derivatives.

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- Definition

Amount of credit risk valuation adjustment to derivative assets to properly reflect the credit quality of the counterparties.

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Amount of credit risk valuation adjustment to derivative liabilities to properly reflect the credit quality of the entity.

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