Long-Term debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Long Term Debt
Long-term Debt	$ 850,191	$ 779,878
Less: current portion	(3,414)	(10,593)
Net carrying amount of the liability component	846,777	769,285
US Credit Agreement Revolving Credit Line [Member]
Long Term Debt
Long-term Debt	132,000
US Credit Agreement Term Loan [Member]
Long Term Debt
Long-term Debt	127,000	134,000
UK Credit Agreement Revolving Credit Line [Member]
Long Term Debt
Long-term Debt	59,060	54,597
UK Credit Agreement Term Loan [Member]
Long Term Debt
Long-term Debt		5,505
UK Credit Agreement Overdraft Line Of Credit [Member]
Long Term Debt
Long-term Debt	13,333	7,116
7.75% senior subordinated notes due 2016 [Member]
Long Term Debt
Long-term Debt	375,000	375,000
3.5% senior subordinated convertible notes due 2026 [Member]
Long Term Debt
Long-term Debt	63,324	148,884
Mortgages [Member]
Long Term Debt
Long-term Debt	75,684	46,052
Other Debt Securities [Member]
Long Term Debt
Long-term Debt	$ 4,790	$ 8,724