| Segment Reporting [Table Text Block] |
| | | As of and for the three months ended June 30, 2026 | |
| | | | | | Retirement and | | | Wealth Advisory | | | Corporate | | | | |
| (dollars in thousands) | | Banking | | | Benefit Services | | | Services | | | Administration | | | Consolidated | |
| Net interest income (loss) | | $ | 48,753 | | | $ | — | | | $ | — | | | $ | (1,041 | ) | | $ | 47,712 | |
| Provision for credit losses | | | 495 | | | | — | | | | — | | | | — | | | | 495 | |
| Noninterest income (loss) | | | 7,039 | | | | 17,347 | | | | 7,705 | | | | 854 | | | | 32,945 | |
| Noninterest expense | | | | | | | | | | | | | | | | | | | | |
| Compensation | | | 12,546 | | | | 7,881 | | | | 3,746 | | | | 1,982 | | | | 26,155 | |
| Employee taxes and benefits | | | 3,159 | | | | 2,214 | | | | 638 | | | | 744 | | | | 6,755 | |
| Business services, software and technology expense | | | 2,679 | | | | 1,577 | | | | 1,051 | | | | 133 | | | | 5,440 | |
| Merger and acquisition expense | | | — | | | | — | | | | — | | | | 6 | | | | 6 | |
| Other noninterest expense | | | 9,873 | | | | 3,405 | | | | 939 | | | | 310 | | | | 14,527 | |
| Total noninterest expense | | | 28,257 | | | | 15,077 | | | | 6,374 | | | | 3,175 | | | | 52,883 | |
| Net income (loss) before taxes | | $ | 27,040 | | | $ | 2,270 | | | $ | 1,331 | | | $ | (3,362 | ) | | $ | 27,279 | |
| Total assets | | $ | 5,182,014 | | | $ | 31,467 | | | $ | 6,477 | | | $ | 68,760 | | | $ | 5,288,718 | |
| | | As of and for the six months ended June 30, 2026 | |
| | | | | | | Retirement and | | | Wealth Advisory | | | Corporate | | | | | |
| (dollars in thousands) | | Banking | | | Benefit Services | | | Services | | | Administration | | | Consolidated | |
| Net interest income (loss) | | $ | 94,298 | | | $ | — | | | $ | — | | | $ | (1,675 | ) | | $ | 92,623 | |
| Provision for credit losses | | | (4,388 | ) | | | — | | | | — | | | | — | | | | (4,388 | ) |
| Noninterest income (loss) | | | 13,387 | | | | 34,754 | | | | 14,942 | | | | 709 | | | | 63,792 | |
| Noninterest expense | | | | | | | | | | | | | | | | | | | | |
| Compensation | | | 24,257 | | | | 15,597 | | | | 6,777 | | | | 3,611 | | | | 50,242 | |
| Employee taxes and benefits | | | 6,286 | | | | 4,352 | | | | 1,384 | | | | 1,373 | | | | 13,395 | |
| Business services, software and technology expense | | | 5,416 | | | | 3,444 | | | | 2,148 | | | | 271 | | | | 11,279 | |
| Merger and acquisition expense | | | — | | | | — | | | | — | | | | (28 | ) | | | (28 | ) |
| Other noninterest expense | | | 19,691 | | | | 6,293 | | | | 1,792 | | | | 610 | | | | 28,386 | |
| Total noninterest expense | | | 55,650 | | | | 29,686 | | | | 12,101 | | | | 5,837 | | | | 103,274 | |
| Net income (loss) before taxes | | $ | 56,423 | | | $ | 5,068 | | | $ | 2,841 | | | $ | (6,803 | ) | | $ | 57,529 | |
| Total assets | | $ | 5,182,014 | | | $ | 31,467 | | | $ | 6,477 | | | $ | 68,760 | | | $ | 5,288,718 | |
| | | As of and for the three months ended June 30, 2025 | |
| | | | | | | Retirement and | | | Wealth Advisory | | | Corporate | | | | | |
| (dollars in thousands) | | Banking | | | Benefit Services | | | Services | | | Administration | | | Consolidated | |
| Net interest income (loss) | | $ | 43,684 | | | $ | — | | | $ | — | | | $ | (652 | ) | | $ | 43,032 | |
| Provision for credit losses | | | — | | | | — | | | | — | | | | — | | | | — | |
| Noninterest income | | | 8,436 | | | | 16,024 | | | | 7,363 | | | | (60 | ) | | | 31,763 | |
| Noninterest expense | | | | | | | | | | | | | | | | | | | | |
| Compensation | | | 12,278 | | | | 7,064 | | | | 3,383 | | | | 1,618 | | | | 24,343 | |
| Employee taxes and benefits | | | 3,289 | | | | 2,015 | | | | 721 | | | | 608 | | | | 6,633 | |
| Business services, software and technology expense | | | 3,084 | | | | 1,930 | | | | 686 | | | | 168 | | | | 5,868 | |
| Merger and acquisition expense | | | — | | | | — | | | | — | | | | 11 | | | | 11 | |
| Other noninterest expense | | | 8,797 | | | | 2,157 | | | | 342 | | | | 287 | | | | 11,583 | |
| Total noninterest expense | | | 27,448 | | | | 13,166 | | | | 5,132 | | | | 2,692 | | | | 48,438 | |
| Net income (loss) before taxes | | $ | 24,672 | | | $ | 2,858 | | | $ | 2,231 | | | $ | (3,404 | ) | | $ | 26,357 | |
| Total assets | | $ | 5,244,506 | | | $ | 30,817 | | | $ | 6,055 | | | $ | 42,444 | | | $ | 5,323,822 | |
| | | As of and for the six months ended June 30, 2025 | |
| | | | | | | Retirement and | | | Wealth Advisory | | | Corporate | | | | | |
| (dollars in thousands) | | Banking | | | Benefit Services | | | Services | | | Administration | | | Consolidated | |
| Net interest income (loss) | | $ | 85,491 | | | $ | — | | | $ | — | | | $ | (1,302 | ) | | $ | 84,189 | |
| Provision for credit losses | | | 863 | | | | — | | | | — | | | | — | | | | 863 | |
| Noninterest income | | | 13,083 | | | | 32,130 | | | | 14,267 | | | | (85 | ) | | | 59,395 | |
| Noninterest expense | | | | | | | | | | | | | | | | | | | | |
| Compensation | | | 23,914 | | | | 14,280 | | | | 6,435 | | | | 2,675 | | | | 47,304 | |
| Employee taxes and benefits | | | 7,169 | | | | 4,326 | | | | 1,462 | | | | 1,439 | | | | 14,396 | |
| Business services, software and technology expense | | | 6,048 | | | | 3,924 | | | | 1,304 | | | | 344 | | | | 11,620 | |
| Merger and acquisition expense | | | — | | | | — | | | | — | | | | 297 | | | | 297 | |
| Other noninterest expense | | | 19,528 | | | | 4,253 | | | | 768 | | | | 639 | | | | 25,188 | |
| Total noninterest expense | | | 56,659 | | | | 26,783 | | | | 9,969 | | | | 5,394 | | | | 98,805 | |
| Net income (loss) before taxes | | $ | 41,052 | | | $ | 5,347 | | | $ | 4,298 | | | $ | (6,781 | ) | | $ | 43,916 | |
| Total assets | | $ | 5,244,506 | | | $ | 30,817 | | | $ | 6,055 | | | $ | 42,444 | | | $ | 5,323,822 | |
|