Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 23,211	$ 16,170	$ 15,029	$ 13,910	$ 2,989	$ 11,897	$ 13,589	$ 12,079	$ 68,320	$ 40,554	$ 44,811
Other comprehensive (loss) income, net of tax:
Unrealized (losses) gains on available for sale securities arising during the period, after reclassifications									(12,434)	3,165	(6,384)
Change in minimum pension liability, after reclassifications									388	(370)	592
Change in joint beneficiary agreement liability									426	(110)	(343)
Other comprehensive (loss) income									(11,620)	2,685	(6,135)
Comprehensive income									$ 56,700	$ 43,239	$ 38,676