Derivatives (Narrative) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) item
Derivative [Line Items]
Notional amount of derivatives	$ 6,010,689	$ 4,301,969
Available for sale debt securities, Amortized Cost	4,637,610
Fair value liability	5,700	7,300
Credit risk-related contingent features, net liability position	12,900	400
Credit risk-related contingent features, posted collateral	12,400	300
Derivatives Designated as Hedging Instruments [Member]
Derivative [Line Items]
Notional amount of derivatives	1,659,400	1,358,110
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member]
Derivative [Line Items]
Termination fees		10,600
Amortization of accumulated other comprehensive loss on terminated cash flow hedges	4,100	$ 6,000
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member] \| Swap Agreement One To Five [Member]
Derivative [Line Items]
Number of interest rate swap terminated \| item		5
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member] \| Swap Agreement 4, Expires 2021 [Member]
Derivative [Line Items]
Notional amount of derivatives	$ 50,000
Derivative maturity expiration year	2021
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member] \| Swap Agreement 1, Expires 2022 [Member]
Derivative [Line Items]
Notional amount of derivatives	$ 475,000
Derivative maturity expiration year	2022
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member] \| Swap Agreement 2, Expires 2023 [Member]
Derivative [Line Items]
Notional amount of derivatives	$ 550,000
Derivative maturity expiration year	2023
Interest Rate Swaps [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedge [Member] \| Swap Agreement 3, Expires 2024 [Member]
Derivative [Line Items]
Notional amount of derivatives	$ 100,000
Derivative maturity expiration year	2024
Interest Rate Swaps - Securities [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Fair Value Hedging [Member]
Derivative [Line Items]
Notional amount of derivatives	$ 441,400
Interest Rate Swaps - Securities [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Fair Value Hedging [Member] \| Commercial Mortgage-Backed Securities [Member]
Derivative [Line Items]
Available for sale debt securities, Amortized Cost	498,300
Interest Rate Swaps - Securities [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Fair Value Hedging [Member] \| Other Liabilities [Member]
Derivative [Line Items]
Basis adjustment to interest rate swaps	$ 300

Derivative instruments basis adjustment to interest rate swaps.

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- Definition

Derivative, Maturity Year

+ References

No definition available.

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- Definition

Number of interest rate derivatives terminated.

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Termination Fees To Settle Interest Rate Swap Liabilities

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- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
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- Definition

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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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.

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No definition available.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

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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
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Fair value of financial and nonfinancial obligations.

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Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

+ References

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