CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 41,204	$ 46,992	$ 45,868
Other comprehensive income (loss), net of tax:
Net change in unrealized gain (loss) on investment securities	344	(4,452)	(4,405)
Minimum pension liability adjustment	138	2,728	1,449
Total other comprehensive income (loss), net of tax	482	(1,724)	(2,956)
Comprehensive income	$ 41,686	$ 45,268	$ 42,912