Regulatory Capital - Summary of the Bank's Compliance (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Tier I (leverage) capital:
Tier i (leverage) capital, capital level, amount	$ 683,521	$ 680,749
Tier i (leverage) capital, capital level, percent	9.56%	9.65%
Tier i (leverage) capital, requirement to be well capitalized, amount	$ 357,421	$ 352,581
Tier i (leverage) capital, requirement to be well capitalized, percent	5.00%	5.00%
Tier i (leverage) capital, excess, amount	$ 326,100	$ 328,168
Tier i (leverage) capital, excess, percent	4.56%	4.65%
Common Equity Tier I risk-based capital:
Common equity tier i risk-based capital, capital level, amount	$ 683,521	$ 680,749
Common equity tier i risk-based capital, capital level, percent	12.63%	13.02%
Common equity tier i risk-based capital, requirement to be well capitalized, amount	$ 351,803	$ 339,944
Common equity tier i risk-based capital, requirement to be well capitalized, percent	6.50%	6.50%
Common equity tier i risk-based capital, excess, amount	$ 331,718	$ 340,805
Common equity tier i risk-based capital, excess, percent	6.13%	6.52%
Tier I risk-based capital:
Tier 1 risk-based capital, capital level, amount	$ 683,521	$ 680,749
Tier 1 risk-based capital, capital level, percent	12.63%	13.02%
Tier 1 risk-based capital, requirement to be well capitalized, amount	$ 432,988	$ 418,393
Tier 1 risk-based capital, requirement to be well capitalized, percent	8.00%	8.00%
Tier 1 risk-based capital, excess, amount	$ 250,533	$ 262,356
Tier 1 risk-based capital, excess, percent	4.63%	5.02%
Total risk-based capital:
Total risk-based capital, capital level, amount	$ 717,192	$ 702,500
Total risk-based capital, capital level, percent	13.25%	13.43%
Total risk-based capital, requirement to be well capitalized, amount	$ 541,235	$ 522,991
Total risk-based capital, requirement to be well capitalized, percent	10.00%	10.00%
Total risk-based capital, excess, amount	$ 175,957	$ 179,509
Total risk-based capital, excess, percent	3.25%	3.43%
Holding Company
Tier I (leverage) capital:
Tier i (leverage) capital, capital level, amount	$ 617,620	$ 615,500
Tier i (leverage) capital, capital level, percent	8.64%	8.73%
Tier i (leverage) capital, requirement to be well capitalized, amount	$ 357,349	$ 352,581
Tier i (leverage) capital, requirement to be well capitalized, percent	5.00%	5.00%
Tier i (leverage) capital, excess, amount	$ 260,271	$ 262,919
Tier i (leverage) capital, excess, percent	3.64%	3.73%
Common Equity Tier I risk-based capital:
Common equity tier i risk-based capital, capital level, amount	$ 583,238	$ 572,651
Common equity tier i risk-based capital, capital level, percent	10.79%	10.95%
Common equity tier i risk-based capital, requirement to be well capitalized, amount	$ 351,397	$ 339,929
Common equity tier i risk-based capital, requirement to be well capitalized, percent	6.50%	6.50%
Common equity tier i risk-based capital, excess, amount	$ 231,841	$ 232,722
Common equity tier i risk-based capital, excess, percent	4.29%	4.45%
Tier I risk-based capital:
Tier 1 risk-based capital, capital level, amount	$ 617,620	$ 615,500
Tier 1 risk-based capital, capital level, percent	11.42%	11.77%
Tier 1 risk-based capital, requirement to be well capitalized, amount	$ 432,488	$ 418,374
Tier 1 risk-based capital, requirement to be well capitalized, percent	8.00%	8.00%
Tier 1 risk-based capital, excess, amount	$ 185,132	$ 197,126
Tier 1 risk-based capital, excess, percent	3.42%	3.77%
Total risk-based capital:
Total risk-based capital, capital level, amount	$ 726,291	$ 712,251
Total risk-based capital, capital level, percent	13.43%	13.62%
Total risk-based capital, requirement to be well capitalized, amount	$ 540,610	$ 522,967
Total risk-based capital, requirement to be well capitalized, percent	10.00%	10.00%
Total risk-based capital, excess, amount	$ 185,681	$ 189,284
Total risk-based capital, excess, percent	3.43%	3.62%