Fair Value Assets and Liabilities measured on nonrecurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carried at fair value	$ 6,924	$ 2,090
Loans Receivable, Fair Value Disclosure	7,112,474	6,441,458
Servicing Asset at Fair Value, Amount	12,200	5,800
Other Assets, Fair Value Disclosure	7,072,339	6,426,869
Other Repossessed Assets	3,600	4,200
Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	6,924	2,090
Servicing Asset at Fair Value, Amount	12,179	5,797
Other Assets, Fair Value Disclosure	735	3,033
Other Repossessed Assets	3,164	3,599
Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	175	217
Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	6,749	1,873
Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	735	738
Nonrecurring basis | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	2,295
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Repossessed Assets	0
Level 1 | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 1 | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	33,211	12,499
Level 2 | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset at Fair Value, Amount	12,179	5,797
Other Assets, Fair Value Disclosure	0	0
Level 2 | Nonrecurring basis | Other Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Repossessed Assets	0
Level 2 | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Level 2 | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans carried at fair value	6,924	2,090
Loans Receivable, Fair Value Disclosure	7,079,263	6,428,959
Other Assets, Fair Value Disclosure	7,072,339	6,426,869
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	6,924	2,090
Other Assets, Fair Value Disclosure	735	3,033
Other Repossessed Assets	3,164	3,599
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	175	217
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Commercial Real Estate Portfolio Segment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	6,749	1,873
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	735	738
Fair Value, Inputs, Level 3 [Member] | Nonrecurring basis | Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Assets, Fair Value Disclosure	$ 0	$ 2,295