Accumulated Other Comprehensive Income Changes in AOCI (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (2,616)	$ (10,840)
Other comprehensive income (loss) before reclassifications	(76,608)	6,543
Amounts reclassified from accumulated other comprehensive loss	(209)	1,681
Net other comprehensive income (loss) for the year	(76,817)	8,224	(1,770)
Accumulated other comprehensive income (loss), ending balance	(79,433)	(2,616)	(10,840)
Benefits Liability, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(6,696)	(16,351)
Other comprehensive income (loss) before reclassifications	(17,314)	7,986
Amounts reclassified from accumulated other comprehensive loss	568	1,669
Net other comprehensive income (loss) for the year	(16,746)	9,655
Accumulated other comprehensive income (loss), ending balance	(23,442)	(6,696)
Cumulative Foreign Currency Exchange
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	3,904	5,511
Other comprehensive income (loss) before reclassifications	(60,128)	(1,607)
Amounts reclassified from accumulated other comprehensive loss	0	0
Net other comprehensive income (loss) for the year	(60,128)	(1,607)
Accumulated other comprehensive income (loss), ending balance	(56,224)	3,904
Net Unrealized Holding Gains on Investments, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	176	0
Other comprehensive income (loss) before reclassifications	834	164
Amounts reclassified from accumulated other comprehensive loss	(777)	12
Net other comprehensive income (loss) for the year	57	176
Accumulated other comprehensive income (loss), ending balance	$ 233	$ 176