Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of accumulated other comprehensive loss
Balance at the beginning of the period	$ (13,842)	$ (13,130)	$ (7,484)
Other comprehensive income before reclassifications	5,890	(2,322)	(5,765)
Amounts reclassified from accumulated other comprehensive income	501	1,093	563
Currency translation	(1,889)	517	(444)
Net current period other comprehensive income	4,502	(712)	(5,646)
Balance at the end of the period	(9,340)	(13,842)	(13,130)
Unrecognized Prior Service Cost
Components of accumulated other comprehensive loss
Balance at the beginning of the period	825	378	380
Other comprehensive income before reclassifications		375
Amounts reclassified from accumulated other comprehensive income	(172)	72	(2)
Net current period other comprehensive income	(172)	447	(2)
Balance at the end of the period	653	825	378
Unrecognized Loss
Components of accumulated other comprehensive loss
Balance at the beginning of the period	(17,399)	(15,723)	(10,523)
Other comprehensive income before reclassifications	5,890	(2,697)	(5,765)
Amounts reclassified from accumulated other comprehensive income	673	1,021	565
Net current period other comprehensive income	6,563	(1,676)	(5,200)
Balance at the end of the period	(10,836)	(17,399)	(15,723)
Foreign Currency Translation
Components of accumulated other comprehensive loss
Balance at the beginning of the period	2,732	2,215	2,659
Currency translation	(1,889)	517	(444)
Net current period other comprehensive income	(1,889)	517	(444)
Balance at the end of the period	$ 843	$ 2,732	$ 2,215