Consolidated Statements of Comprehensive Income - Parenthetical - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification adjustment for (gain) loss on derivative instruments included in net income, tax	$ 56	$ 60	$ 114	$ 121
Amortization of postretirement liability losses included in net periodic benefit cost, tax	150	420	(819)	649
Foreign currency translation adjustments recognized during the period, tax	19	6	33	(63)
Reclassification adjustment for foreign currency translation (gain) loss included in net income, tax	0	0	0	491
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	(16)	(23)	(10)	(34)
Reclassification adjustment for loss (gain) on available-for-sale investments included in net income, tax	$ 19	$ 15	$ 37	$ 34