Fair Value by Balance Sheet grouping (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 370,474,000	$ 159,956,000
Investment Owned, at Fair Value	1,059,341,000	1,209,701,000
Mortgages Held-for-sale, Fair Value Disclosure	31,666,000	12,278,000
Derivative Asset	1,545,000	221,000
Impaired loans carried at fair value	6,924,000	2,090,000
Other Assets, Fair Value Disclosure	7,072,339,000	6,426,869,000
Loans Receivable, Fair Value Disclosure	7,112,474,000	6,441,458,000
Time Deposits, Fair Value	870,804,000	1,145,537,000
Other Liabilities, Fair Value Disclosure	1,379,000	1,273,000
Deposits, Fair Value Disclosure	872,183,000	1,146,810,000
Short-term Debt, Fair Value	342,230,000	230,657,000
Long-term Debt, Fair Value	31,376,000	200,726,000
Subordinated Debt Obligations, Fair Value Disclosure	179,147,000	14,372,000
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	885,000	575,000
Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment Owned, at Fair Value	2,511,000	1,993,000
Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Swaps, fair value	3,934,000	1,870,000
Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		1,870,000
Swaps, fair value	226,000	226,000
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	370,474,000	159,956,000
Derivative Asset	0	0
Loans Receivable, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure	1,379,000	1,273,000
Deposits, Fair Value Disclosure	1,379,000	1,273,000
Level 1 | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment Owned, at Fair Value	2,026,000	1,537,000
Level 1 | Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment Owned, at Fair Value	1,059,341,000	1,209,701,000
Mortgages Held-for-sale, Fair Value Disclosure	31,666,000	12,278,000
Derivative Asset	1,545,000	221,000
Loans Receivable, Fair Value Disclosure	33,211,000	12,499,000
Time Deposits, Fair Value	870,804,000	1,145,537,000
Deposits, Fair Value Disclosure	870,804,000	1,145,537,000
Short-term Debt, Fair Value	342,230,000	230,657,000
Long-term Debt, Fair Value	31,376,000	200,726,000
Subordinated Debt Obligations, Fair Value Disclosure	179,147,000	14,372,000
Level 2 | Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	3,934,000
Swaps, fair value	3,934,000	1,870,000
Level 2 | Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		1,870,000
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	885,000	575,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0	0
Impaired loans carried at fair value	6,924,000	2,090,000
Other Assets, Fair Value Disclosure	7,072,339,000	6,426,869,000
Loans Receivable, Fair Value Disclosure	7,079,263,000	6,428,959,000
Deposits, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment Owned, at Fair Value	485,000	456,000
Fair Value, Inputs, Level 3 [Member] | Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	0
Fair Value, Inputs, Level 3 [Member] | Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Swaps, fair value	226,000	226,000
Unrealized Gain (Loss) on Cash Flow Hedging Instruments	0	0
Estimate of Fair Value Measurement [Member] | Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	3,934,000
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	370,474,000	159,956,000
Investment Owned, at Fair Value	1,059,341,000	1,209,701,000
Mortgages Held-for-sale, Fair Value Disclosure	31,666,000	12,278,000
Derivative Asset	1,545,000	221,000
Impaired loans carried at fair value	6,924,000	2,090,000
Other Assets, Fair Value Disclosure	7,051,975,000	6,430,136,000
Loans Receivable, Fair Value Disclosure	7,092,110,000	6,444,725,000
Time Deposits, Fair Value	864,573,000	1,139,131,000
Other Liabilities, Fair Value Disclosure	1,379,000	1,273,000
Deposits, Fair Value Disclosure	865,952,000	1,140,404,000
Short-term Debt, Fair Value	342,230,000	230,657,000
Long-term Debt, Fair Value	32,500,000	192,500,000
Subordinated Debt Obligations, Fair Value Disclosure	187,774,000	15,000,000
Reported Value Measurement [Member] | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment Owned, at Fair Value	2,511,000	1,993,000
Reported Value Measurement [Member] | Loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset	3,934,000
Swaps, fair value	3,934,000	1,870,000
Reported Value Measurement [Member] | Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		1,870,000
Swaps, fair value	$ 226,000	$ 226,000