Long-Term Debt (Details)			3 Months Ended	9 Months Ended		3 Months Ended			3 Months Ended					9 Months Ended			3 Months Ended					0 Months Ended		1 Months Ended				1 Months Ended		1 Months Ended	3 Months Ended
	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2012 US Credit Agreement Revolving Credit Line USD ($)	Sep. 30, 2012 US Credit Agreement Revolving Credit Line USD ($)	Dec. 31, 2011 US Credit Agreement Revolving Credit Line USD ($)	Sep. 30, 2012 US Credit Agreement Term Loan USD ($)	Dec. 31, 2011 US Credit Agreement Term Loan USD ($)	Sep. 30, 2012 US Credit Agreement Letters of Credit USD ($)	Sep. 30, 2012 UK Credit Agreement Revolving Credit Line USD ($)	Sep. 30, 2012 UK Credit Agreement Revolving Credit Line GBP (£)	Dec. 31, 2011 UK Credit Agreement Revolving Credit Line USD ($)	Sep. 30, 2012 UK Credit Agreement Revolving Credit Line Minimum	Sep. 30, 2012 UK Credit Agreement Revolving Credit Line Maximum	Sep. 30, 2012 U.K. acquisition term loan GBP (£)	Sep. 30, 2012 U.K. acquisition term loan USD ($)	Jan. 31, 2012 U.K. acquisition term loan GBP (£)	Sep. 30, 2012 U.K. acquisition term loan Minimum	Sep. 30, 2012 U.K. acquisition term loan Maximum	Sep. 30, 2012 UK Credit Agreement Overdraft Line of Credit USD ($)	Sep. 30, 2012 UK Credit Agreement Overdraft Line of Credit GBP (£)	Dec. 31, 2011 UK Credit Agreement Overdraft Line of Credit USD ($)	Jun. 25, 2012 3.5% senior subordinated convertible notes due 2026 USD ($)	Jun. 21, 2012 3.5% senior subordinated convertible notes due 2026 USD ($) item	Jul. 31, 2012 3.5% senior subordinated convertible notes due 2026 USD ($)	May 31, 2012 3.5% senior subordinated convertible notes due 2026	Sep. 30, 2012 3.5% senior subordinated convertible notes due 2026	Dec. 31, 2011 3.5% senior subordinated convertible notes due 2026 USD ($)	Aug. 31, 2012 5.75% senior subordinated notes due 2022 USD ($)	Sep. 30, 2012 5.75% senior subordinated notes due 2022 USD ($)	Aug. 31, 2012 5.75% senior subordinated notes due 2022 Debt redemption prior to October 1, 2015	Sep. 30, 2012 7.75% senior subordinated notes due 2016 USD ($)	Dec. 31, 2011 7.75% senior subordinated notes due 2016 USD ($)	Sep. 30, 2012 Mortgages USD ($)	Dec. 31, 2011 Mortgages USD ($)	Sep. 30, 2012 Other Debt Securities USD ($)	Dec. 31, 2011 Other Debt Securities USD ($)
Long Term Debt
Long-term Debt	$ 830,847,000	$ 850,191,000			$ 132,000,000	$ 110,000,000	$ 127,000,000		$ 45,256,000		$ 59,060,000			£ 25,500,000	$ 41,216,000				$ 3,113,000		$ 13,333,000						$ 63,324,000		$ 550,000,000			$ 375,000,000	$ 73,549,000	$ 75,684,000	$ 7,713,000	$ 4,790,000
Less: current portion	(14,929,000)	(3,414,000)
Net long-term debt	815,918,000	846,777,000
Interest rate (as a percent)																										3.50%			5.75%		7.75%	7.75%
Principal amount redeemed																															375,000,000
Percentage of principal amount at which the entity may redeem some or all of the notes																									100.00%
Conversion rate of convertible notes																							42.7796
Conversion price per share (in dollars per share)																							$ 23.38
Conversion maximum threshold amount for holder to receive payment in cash equal to the lessor of (i) $1,000 or (ii) The conversion value																							1,000
Conversion minimum threshold amount for the holder to receive payment of cash, common stock or a combination of two																							1,000
Outstanding principal amount of convertible notes																						25,546,000
Settlement of remaining principal and interest on convertible notes in cash																						37,778,000
Conversion balance paid in cash																								24,909,000
Maximum credit available			375,000,000	375,000,000				10,000,000		100,000,000						30,000,000				10,000,000
Base rate of interest on loans			LIBOR			LIBOR			LIBOR	LIBOR									Bank of England Base Rate	Bank of England Base Rate
Line of credit basis spread on variable rate (as a percent)			2.50%	2.50%		2.50%			1.35%	1.35%		1.35%	3.00%						1.75%	1.75%
Incremental interest rate for uncollateralized borrowings in excess of maximum limit (as a percent)				1.00%
Letters of credit outstanding	18,997,000							500,000
Repayment of term loan, quarterly installments														1,500,000
Frequency of principal repayments														Quarterly
Final payment due December 31, 2015														7,500,000
Low end of interest rate, depending on UK subsidiaries ratios																	2.675%
High end of interest rate, depending on UK subsidiaries ratios																		4.325%
Debt issued																												550,000,000
Specified equity offerings, percentage of debt which may be redeemed																														40.00%
Change of control, redemption price as a percentage of principal																												101.00%
Sale of assets, redemption price as percentage of principal																												100.00%
Balance outstanding under credit agreement									48,369,000	29,926,000
Pre-tax expense on the extinguishment of debt																															17,753,000
Redemption premium																															15,755,000
Write off of unamortized deferred financing costs																															$ 1,998,000