Derivatives and Balance Sheet Offsetting - Collateral pledged table (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Balance Sheet Offsetting [Line Items]
Repurchase agreements, amounts offset in balance sheet	$ 0	$ 0
Repurchase agreements, net amount presented in statement of financial position	26,966	64,437
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	(26,966)	(64,437)
Securities sold under agreements to repurchase, amount not offset	0	0
Interest Rate Contracts [Member]
Balance Sheet Offsetting [Line Items]
Derivative Assets, Gross Amounts Offset in the Balance Sheets	0	0
Derivative Asset	53,202	19,144
Derivative, Collateral, Obligation to Return Cash	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	53,202	19,144
Derivative Liability, Gross Amounts Offset in Balance Sheets	0	0
Derivative Liability	53,677	19,145
Derivative, Collateral, Right to Reclaim Cash	53,677	19,145
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0	0
Interest rate collar [Domain]
Balance Sheet Offsetting [Line Items]
Derivative Assets, Gross Amounts Offset in the Balance Sheets	0	0
Derivative Asset	35,668	14,727
Derivative, Collateral, Obligation to Return Cash	(35,668)	(14,727)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Available-for-sale Securities [Member]
Balance Sheet Offsetting [Line Items]
Securities Sold under Agreements to Repurchase, Gross	26,966	64,437
Not Designated as Hedging Instrument [Member] \| Interest Rate Contracts [Member]
Balance Sheet Offsetting [Line Items]
Fair value of asset derivative instruments	53,202	19,144
Fair value of liability derivative instruments	53,677	19,145
Designated as Hedging Instrument [Member] \| Interest rate collar [Domain]
Balance Sheet Offsetting [Line Items]
Fair value of asset derivative instruments	$ 35,668	$ 14,727

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