Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 23,657	$ 17,606	$ 7,430	$ 16,121	$ 22,890	$ 23,395	$ 23,061	$ 22,726	$ 64,814	$ 92,072	$ 68,320
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available for sale securities arising during the period, after reclassifications									11,126	17,159	(12,434)
Change in minimum pension liability, after reclassifications									6,972	(4,502)	388
Change in joint beneficiary agreement liability									(596)	0	426
Other comprehensive income (loss)									17,502	12,657	(11,620)
Comprehensive income									$ 82,316	$ 104,729	$ 56,700