Allowance for Loan Losses - Accrual and Non-Accrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Non-Accrual Loans, Loan Balance
Loan Balance	$ 49,773	$ 87,479
Non-Accrual Loans, %
Total Loans, Net of Unearned Income	5,409,440	5,842,337
Real estate loans
Non-Accrual Loans, Loan Balance
Loan Balance	21,076	43,041
Non-Accrual Loans, %
Total Loans, Net of Unearned Income	4,006,392	4,424,031
Consumer loans and overdrafts
Accrual Loans, Loan Balance
Loan Balance	$ 423,408	$ 246,887	$ 88,050
Accrued Loans, %
%	99.94%	99.91%	99.53%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 257	$ 233	$ 416
Non-Accrual Loans, %
%	0.06%	0.09%	0.47%
Total Loans, Net of Unearned Income	$ 423,665	$ 247,120	$ 88,466
%	100.00%	100.00%	100.00%
Consumer loans and overdrafts | Current
Accrual Loans, Loan Balance
Loan Balance	$ 423,373	$ 246,794	$ 87,656
Accrued Loans, %
%	99.93%	99.88%	99.08%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 251	$ 203	$ 374
Non-Accrual Loans, %
%	0.06%	0.08%	0.42%
Consumer loans and overdrafts | Noncurrent
Accrual Loans, Loan Balance
Loan Balance	$ 35	$ 93	$ 394
Accrued Loans, %
%	0.01%	0.03%	0.45%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 6	$ 30	$ 42
Non-Accrual Loans, %
%	0.00%	0.01%	0.05%
Consumer loans and overdrafts | 30-59 Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 22	$ 85	$ 215
Accrued Loans, %
%	0.01%	0.03%	0.24%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 0	$ 0	$ 0
Non-Accrual Loans, %
%	0.00%	0.00%	0.00%
Consumer loans and overdrafts | 60-89 Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 5	$ 6	$ 174
Accrued Loans, %
%	0.00%	0.00%	0.20%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 2	$ 0	$ 2
Non-Accrual Loans, %
%	0.00%	0.00%	0.00%
Consumer loans and overdrafts | 90+ Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 8	$ 2	$ 5
Accrued Loans, %
%	0.00%	0.00%	0.01%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 4	$ 30	$ 40
Non-Accrual Loans, %
%	0.00%	0.01%	0.05%
Single-family residential | Real estate loans
Accrual Loans, Loan Balance
Loan Balance	$ 656,213	$ 628,902	$ 531,811
Accrued Loans, %
%	99.23%	98.33%	98.65%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 5,126	$ 10,667	$ 7,291
Non-Accrual Loans, %
%	0.77%	1.67%	1.35%
Total Loans, Net of Unearned Income	$ 661,339	$ 639,569	$ 539,102
%	100.00%	100.00%	100.00%
Single-family residential | Real estate loans | Current
Accrual Loans, Loan Balance
Loan Balance	$ 655,270	$ 626,468	$ 526,497
Accrued Loans, %
%	99.09%	97.95%	97.67%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 2,612	$ 5,333	$ 3,902
Non-Accrual Loans, %
%	0.39%	0.83%	0.72%
Single-family residential | Real estate loans | Noncurrent
Accrual Loans, Loan Balance
Loan Balance	$ 943	$ 2,434	$ 5,314
Accrued Loans, %
%	0.14%	0.38%	0.98%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 2,514	$ 5,334	$ 3,389
Non-Accrual Loans, %
%	0.38%	0.84%	0.63%
Single-family residential | Real estate loans | 30-59 Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 531	$ 1,807	$ 4,332
Accrued Loans, %
%	0.08%	0.28%	0.80%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 459	$ 1,336	$ 253
Non-Accrual Loans, %
%	0.07%	0.21%	0.05%
Single-family residential | Real estate loans | 60-89 Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 412	$ 627	$ 982
Accrued Loans, %
%	0.06%	0.10%	0.18%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 0	$ 44	$ 266
Non-Accrual Loans, %
%	0.00%	0.01%	0.05%
Single-family residential | Real estate loans | 90+ Days Past Due
Accrual Loans, Loan Balance
Loan Balance	$ 0	$ 0	$ 0
Accrued Loans, %
%	0.00%	0.00%	0.00%
Non-Accrual Loans, Loan Balance
Loan Balance	$ 2,055	$ 3,954	$ 2,870
Non-Accrual Loans, %
%	0.31%	0.62%	0.53%