Pension and Other Post-Retirement Plans (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
U.K. Plan
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	$ 43,943,000
Fair value of assets at end of year	42,538,000	43,943,000
Expected benefit payments
2012	824,000
2013	839,000
2014	870,000
2015	901,000
2016	917,000
2017-2021	5,051,000
Weighted average actuarial assumptions used to determine the benefit obligation and net periodic benefit cost
Discount rate used to calculate benefit obligation (as a percent)	4.80%	5.40%	5.80%
Discount rate used to calculate net periodic pension cost (as a percent)	5.40%	5.80%	6.20%
Rate of compensation increase (as a percent)	3.50%	4.00%	3.60%
Expected return on assets (as a percent)	7.50%	7.80%	6.62%
Canadian Plan
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	29,257,000
Fair value of assets at end of year	30,658,000	29,257,000
Expected benefit payments
2012	1,244,000
2013	1,352,000
2014	1,391,000
2015	1,499,000
2016	1,611,000
2017-2021	10,571,000
Weighted average actuarial assumptions used to determine the benefit obligation and net periodic benefit cost
Discount rate used to calculate benefit obligation (as a percent)	5.30%	5.50%	6.40%
Discount rate used to calculate net periodic pension cost (as a percent)	5.50%	6.40%	7.50%
Rate of compensation increase (as a percent)	3.25%	3.25%	3.25%
Expected return on assets (as a percent)	7.00%	7.00%	7.00%
Significant Unobservable Inputs (Level 3) | U.K. Plan
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	2,416,000	1,686,000
Purchases	6,616,000	507,000
Unrealized gain on asset still held, at end of year	324,000	223,000
Fair value of assets at end of year	$ 2,416,000	$ 2,416,000