CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Unrealized gain (loss) on available-for-sale securities, tax	$ 37	$ 11	$ 47	$ 4
Actuarial gain (loss), tax	271	0	200	0
Amortization of prior service cost and actuarial loss for retirement plan included in net periodic pension costs, tax	$ 142	$ 157	$ 302	$ 258