Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) |
3 Months Ended | |
|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
|
| Changes in accumulated other comprehensive (loss) income by component, net of tax | ||
| Balance | $ 945,606,000 | $ 910,619,000 |
| Other comprehensive income | 14,664,000 | 5,067,000 |
| Amounts reclassified out of AOCI | 0 | 0 |
| Balance | 912,568,000 | 900,572,000 |
| Accumulated Other Comprehensive Loss | ||
| Changes in accumulated other comprehensive (loss) income by component, net of tax | ||
| Balance | 2,283,000 | (9,460,000) |
| Balance | 16,947,000 | (4,393,000) |
| Investment Securities Available-for-Sale | ||
| Changes in accumulated other comprehensive (loss) income by component, net of tax | ||
| Balance | 2,199,000 | (9,712,000) |
| Other comprehensive income | 14,664,000 | 5,067,000 |
| Balance | 16,863,000 | (4,645,000) |
| Postretirement Benefits | ||
| Changes in accumulated other comprehensive (loss) income by component, net of tax | ||
| Balance | 84,000 | 252,000 |
| Other comprehensive income | 0 | 0 |
| Balance | $ 84,000 | $ 252,000 |