Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 15,029	$ 13,910	$ 2,989	$ 11,897	$ 13,589	$ 12,079	$ 28,939	$ 25,668
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available for sale securities arising during the period	(3,998)				2,846		(15,024)	3,303
Change in minimum pension liability	80				55		160	109
Other comprehensive income (loss)	(3,918)				2,901		(14,864)	3,412
Comprehensive income	$ 11,111				$ 16,490		$ 14,075	$ 29,080