v3.25.2
Accumulated Other Comprehensive Income (Accumulated Other Comprehensive Income Or Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Accumulated Other Comprehensive Income [Roll Forward]        
Balance at the beginning of the period $ 4,052,898 $ 3,864,707 $ 4,099,729 $ 3,890,652
Other comprehensive income (loss) before reclassification:        
Unrealized gains (losses) (56,618) (19,131) (41,143) 5,061
Total other comprehensive income (loss) (56,680) (18,962) (41,189) 5,230
Balance at the end of the period 4,095,229 4,134,709 4,095,229 4,134,709
Total AOCI [Member]        
Accumulated Other Comprehensive Income [Roll Forward]        
Balance at the beginning of the period (124,471) (94,779) (139,962) (118,971)
Other comprehensive income (loss) before reclassification:        
Unrealized gains (losses) (56,618) (19,131) (41,143) 5,061
Impact of settlements - defined benefit pension plan (62) 169 (46) 169
Total other comprehensive income (loss) (56,680) (18,962) (41,189) 5,230
Balance at the end of the period (181,151) (113,741) (181,151) (113,741)
Net Unrealized Gain (Loss) on Available-for-Sale Securities [Member]        
Accumulated Other Comprehensive Income [Roll Forward]        
Balance at the beginning of the period (124,630) (94,752) (140,105) (118,944)
Other comprehensive income (loss) before reclassification:        
Unrealized gains (losses) (56,618) (19,131) (41,143) 5,061
Total other comprehensive income (loss) (56,618) (19,131) (41,143) 5,061
Balance at the end of the period (181,248) (113,883) (181,248) (113,883)
Defined Benefit Pension Plan [Member]        
Accumulated Other Comprehensive Income [Roll Forward]        
Balance at the beginning of the period 159 (27) 143 (27)
Other comprehensive income (loss) before reclassification:        
Impact of settlements - defined benefit pension plan (62) 169 (46) 169
Total other comprehensive income (loss) (62) 169 (46) 169
Balance at the end of the period $ 97 $ 142 $ 97 $ 142