Pensions (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Multi-Employer Plan
Liability under multi-employer plan	$ 800,000		$ 800,000		$ 1,700,000
Reduction in liability under multi-employer plan	(900,000)
U.S. Plans
Components of net periodic pension costs of the plans
Service cost	292,000	265,000	583,000	530,000
Interest cost	1,127,000	1,164,000	2,254,000	2,380,000
Expected return on plan assets	(1,667,000)	(1,522,000)	(3,334,000)	(3,081,000)
Amortization of prior service cost	19,000	(6,000)	38,000	13,000
Net actuarial loss amortization	909,000	876,000	1,818,000	1,710,000
Net periodic pension cost	680,000	777,000	1,359,000	1,552,000
Expected long-term rate of return on plan assets (as a percent)			7.75%
Employer contributions, 2013					1,300,000
Employer contributions			500,000
Expected employer contribution to pension plans over the balance of current year	800,000		800,000
European Plans
Components of net periodic pension costs of the plans
Service cost	79,000	42,000	157,000	84,000
Interest cost	382,000	439,000	756,000	878,000
Expected return on plan assets	(394,000)	(325,000)	(631,000)	(650,000)
Net actuarial loss amortization	126,000	4,000	102,000	8,000
Foreign currency translation	2,000	(2,000)	8,000	(1,000)
Net periodic pension cost	195,000	158,000	392,000	319,000
Employer contributions, 2013					2,100,000
Employer contributions			700,000
Expected employer contribution to pension plans over the balance of current year	$ 1,400,000		$ 1,400,000
European Plans | Minimum
Components of net periodic pension costs of the plans
Expected long-term rate of return on plan assets (as a percent)			4.50%
European Plans | Maximum
Components of net periodic pension costs of the plans
Expected long-term rate of return on plan assets (as a percent)			5.40%