Other Comprehensive Income (Loss) - Summary of Unrealized Gains and Losses on Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of year	$ 238,737	$ 234,155	$ 228,184	$ 223,726	$ 219,440	$ 216,584	$ 215,257	$ 212,508	$ 223,726	$ 212,508	$ 191,542
Other comprehensive gain (loss)	535	(1,257)	362	(1,312)	367	(1,186)	(2,176)	(629)	(1,672)	(3,624)	7,369
Balance at end of year	245,657	$ 238,737	$ 234,155	228,184	223,726	$ 219,440	$ 216,584	215,257	245,657	223,726	212,508
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of year				$ 28				$ 24	28	24	37
Change in unamortized net actuarial gain (loss)									98	5	(16)
Related deferred taxes									(21)	(1)	3
Other comprehensive gain (loss)									77	4	(13)
Balance at end of year	$ 105				$ 28				$ 105	$ 28	$ 24