Reclassifications from Accumulated Other Comprehensive Income - AOCI Roll Forward (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		$ (6,951)		$ (25,751)		$ (20,082)		$ (25,783)
Other comprehensive income (loss) before reclassifications		(1,175)		3,877		19,273		2,505
Amounts reclassified from accumulated other comprehensive income		10,092		1,255		(17,409)		2,659
Net current-period other comprehensive income		(11,267)		5,132		1,864		5,164
Balance at end of period		(18,218)		(20,619)		(18,218)		(20,619)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period				(201)		(290)		(469)
Other comprehensive income (loss) before reclassifications				(1)				15
Amounts reclassified from accumulated other comprehensive income				0				252
Net current-period other comprehensive income				(1)				267
Net unrealized losses on qualifying cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		314		(5,848)		7,299		(5,654)
Other comprehensive income (loss) before reclassifications		0		4,441		2		3,395
Amounts reclassified from accumulated other comprehensive income		43		959		559		1,811
Net current-period other comprehensive income		(43)		5,400		561		5,206
Balance at end of period		271		(202)		271		(202)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		17,370
Other comprehensive income (loss) before reclassifications		(2,270)				16,004
Amounts reclassified from accumulated other comprehensive income		10,364				(18,567)
Net current-period other comprehensive income		(12,634)				(2,563)
Balance at end of period		4,736		(448)		4,736		(448)
Net unrecognized losses related to pension and severance plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period		(24,635)	[1]	(19,702)	[2]	(27,091)	[1]	(19,660)	[2]
Other comprehensive income (loss) before reclassifications		1,095		(563)		3,267		(905)
Amounts reclassified from accumulated other comprehensive income		(315)		296		599		596
Net current-period other comprehensive income		1,410		(267)		3,866		(309)
Balance at end of period	[1]	$ (23,225)		(19,969)		$ (23,225)		(19,969)
Deferred Tax Liabilities, Other Comprehensive Income				$ 0				$ 0		$ 1	$ 0	$ 0	$ 1

[1] (1) Net of deferred tax asset of $521 thousand, $521 thousand and $401 thousand as of June 30, 2015, March 31, 2015 and December 31, 2014, respectively.

[2] 1) Net of deferred tax liability of $271 thousand, $271 thousand and $530 thousand as of June 30, 2014, March 31, 2014, and December 31, 2013, respectively.