Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 12,533	$ 12,199	$ 9,405	$ 10,674	$ 11,422	$ 12,694	$ 11,366	$ 8,336	$ 44,811	$ 43,818	$ 26,108
Other comprehensive (loss) income, net of tax:
Unrealized holding losses on securities arising during the period									(6,384)	(1,098)	(94)
Change in minimum pension liability									592	1,246	(4,114)
Change in joint beneficiary agreement liability									(343)	277	148
Other comprehensive (loss) income									(6,135)	425	(4,060)
Comprehensive income									$ 38,676	$ 44,243	$ 22,048