Pension and Postretirement Benefits - Summary of funded status of the plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Funded Plans
Change in benefit obligation:
Benefit obligation at beginning of year	$ 15,348	$ 13,938
Service cost	0	0
Interest cost	608	659
Recognized net actuarial loss	(1,530)	1,419
Plan amendments	0	0
Benefits paid	(991)	(668)
Benefit obligation at end of year	13,435	15,348
Change in plan assets:
Fair value of plan assets at beginning of year	10,624	9,846
Actual return on plan assets	580	683
Company contributions	659	763
Benefits paid	(991)	(668)
Fair value of plan assets at end of year	10,872	10,624
Funded status at end of year	(2,563)	(4,724)
Unfunded Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	11,570	10,883
Service cost	66	104
Interest cost	422	491
Recognized net actuarial loss	(856)	799
Plan amendments	0	0
Benefits paid	(666)	(707)
Benefit obligation at end of year	10,536	11,570
Change in plan assets:
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Company contributions	666	707
Benefits paid	(666)	(707)
Fair value of plan assets at end of year	0	0
Funded status at end of year	(10,536)	(11,570)
Postretirement Benefit Plans
Change in benefit obligation:
Benefit obligation at beginning of year	18,701	18,667
Service cost	156	146
Interest cost	663	814
Recognized net actuarial loss	(1,631)	250
Plan amendments	(40)	0
Benefits paid	(930)	(1,176)
Benefit obligation at end of year	16,919	18,701
Change in plan assets:
Fair value of plan assets at beginning of year	1,397	2,118
Actual return on plan assets	(135)	100
Company contributions	188	355
Benefits paid	(930)	(1,176)
Fair value of plan assets at end of year	520	1,397
Funded status at end of year	(16,399)	(17,304)
US Postretirement Benefit Plans
Change in benefit obligation:
Service cost	156	146	128
Interest cost	663	814	868
Recognized net actuarial loss	518	547	533
Change in plan assets:
Fair value of plan assets at end of year	520
Foreign Pension Plans
Change in benefit obligation:
Service cost	534	491	366
Interest cost	702	737	729
Recognized net actuarial loss	248	201	73
Change in plan assets:
Fair value of plan assets at beginning of year	12,997
Fair value of plan assets at end of year	11,560	12,997
Foreign Pension Plans | Funded Plans
Change in benefit obligation:
Benefit obligation at beginning of year	15,387	13,141
Service cost	534	491
Interest cost	582	607
Recognized net actuarial loss	473	(1,086)
Benefits paid	(3,644)	(328)
Translation adjustment	(926)	390
Benefit obligation at end of year	11,460	15,387
Change in plan assets:
Fair value of plan assets at beginning of year	12,997	11,028
Actual return on plan assets	1,148	860
Company contributions	1,892	1,111
Benefits paid	(3,644)	(328)
Translation adjustment	(833)	326
Fair value of plan assets at end of year	11,560	12,997
Funded status at end of year	100	(2,390)
Foreign Pension Plans | Unfunded Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	3,032	2,939
Service cost	0	0
Interest cost	120	130
Recognized net actuarial loss	(44)	(113)
Benefits paid	(219)	(220)
Translation adjustment	(66)	70
Benefit obligation at end of year	2,911	3,032
Change in plan assets:
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Company contributions	219	220
Benefits paid	(219)	(220)
Translation adjustment	0	0
Fair value of plan assets at end of year	0	0
Funded status at end of year	$ (2,911)	$ (3,032)