CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gain (loss) on available-for-sale securities, tax	$ 92	$ 2	$ 139	$ (6)
Actuarial gain (loss), tax	(5)	0	195	0
Amortization of prior service cost and actuarial loss for retirement plan included in net periodic pension costs, tax	$ 141	$ 157	$ 443	$ 401