Consolidated Statements of Comprehensive Income - Parenthetical (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net unrealized gain (loss) on derivative instruments arising during the period, tax	$ 0	$ 52	$ 0	$ (3,116)
Reclassification adjustment for (gain) loss on derivative instruments included in net income, tax	10	(322)	213	(1,948)
Amortization of postretirement liability losses included in net periodic benefit cost, tax	150	543	318	862
Foreign currency translation adjustments arising during the period, tax	26	(234)	54	(197)
Net unrealized gain (loss) on available-for-sale investments arising during the period, tax	4	(77)	5	(100)
Reclassification adjustment for loss (gain) on available-for-sale investments included in net income, tax	$ 17	$ 23	$ 17	$ 42