Reconciliations of fair value measurements using significant unobservable inputs (Level 3) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Rollforward of fair values
Fair value of plan assets at beginning of year	$ 19,652	$ 15,547	$ 14,457
Foreign exchange	538	853	(188)
Actual return on plan assets:
Fair value of plan assets at end of year	23,162	19,652	15,547
Level 3
Rollforward of fair values
Fair value of plan assets at beginning of year	2,046	1,871
Foreign exchange	37	92
Actual return on plan assets:
Assets still held at the reporting date	42	158
Purchases, sales and settlements, net	(80)	(75)
Transfers into or out of Level 3	0	0
Fair value of plan assets at end of year	2,045	2,046
Annuities
Actual return on plan assets:
Fair value of plan assets at end of year	2,045	2,046
Annuities | Level 3
Rollforward of fair values
Fair value of plan assets at beginning of year	2,046	1,871
Foreign exchange	37	92
Actual return on plan assets:
Assets still held at the reporting date	42	158
Purchases, sales and settlements, net	(80)	(75)
Transfers into or out of Level 3	0	0
Fair value of plan assets at end of year	$ 2,045	$ 2,046