Parent company financial statements
 12 Months Ended
Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]  
Parent company financial statements Parent company financial statements: 
 As of December 31,
Balance sheet20202019
Assets  
Cash and cash equivalents(1)
$5,310 $4,673 
Investments:
Equity securities, at fair value1,173 — 
Investment in subsidiaries(1)
1,378,347 782,565 
Other assets12,240 6,292 
Goodwill29 29 
Total assets$1,397,099 $793,559 
Liabilities and shareholders' equity  
Liabilities  
Borrowings$106,299 $30,930 
Accrued expenses and other liabilities(489)300 
Total liabilities105,810 31,230 
Shareholders' equity  
Common stock47,222 31,034 
Additional paid-in capital898,847 425,633 
Retained earnings317,625 293,524 
Accumulated other comprehensive income27,595 12,138 
Total shareholders' equity1,291,289 762,329 
Total liabilities and shareholders' equity$1,397,099 $793,559 
(1) Eliminates in Consolidation
 For the years ended December 31,
Income Statements202020192018
Income
Dividend income from subsidiaries(1)
$49,706 $— $— 
Gain on investments217 — — 
(Loss) gain on other assets— (16)297 
Other income1,732 211 — 
Total income51,655 195 297 
Expenses
Interest expense3,122 1,638 1,651 
Salaries, legal and professional fees1,458 1,056 1,481 
Other noninterest expense283 120 960 
Total expenses4,863 2,814 4,092 
Income (loss) before income tax benefit and equity in undistributed
    earnings of subsidiaries		46,792 (2,619)(3,795)
Federal and state income tax benefit(1,155)(683)(746)
Income (loss) before equity in undistributed earnings of subsidiaries47,947 (1,936)(3,049)
Equity in undistributed earnings from subsidiaries(1)
15,674 85,750 83,285 
Net income$63,621 $83,814 $80,236 
(1) Eliminates in Consolidation
 For the years ended December 31,
Statement of Cash Flows202020192018
Operating Activities   
Net income$63,621 $83,814 $80,236 
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries(15,674)(85,750)(83,285)
Gain on investments(217)— — 
Loss (gain) on other assets— 16 (297)
Stock-based compensation expense10,214 7,089 7,207 
(Increase) decrease in other assets(9,717)1,056 (441)
Decrease in other liabilities(13,363)(9,711)(7,737)
Net provided by (used in) operating activities34,864 (3,486)(4,317)
Investing Activities 
Proceeds from sale of other assets— — 869 
Net cash paid in business combinations (See Note 2)(35,505)— — 
Net cash (used in) provided by investing activities(35,505)— 869 
Financing Activities 
Accretion of interest rate premium on subordinated debt(436)— — 
Payment of dividends(14,264)(10,045)(6,137)
Proceeds of other borrowings15,000 — — 
Net proceeds from sale of common stock978 804 1,196 
Net cash used in financing activities1,278 (9,241)(4,941)
Net decrease in cash and cash equivalents637 (12,727)(8,389)
Cash and cash equivalents at beginning of year4,673 17,400 25,789 
Cash and cash equivalents at end of year$5,310 $4,673 $17,400 
Supplemental noncash disclosures: 
Dividends declared not paid on restricted stock units$238 $149 $226 
Noncash dividend from Bank956 — 572