Intangible Assets (Schedule of Goodwill and Net Carrying Amount of Intangible Assets with Indefinite Lives) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Indefinite-lived Intangible Assets by Segment [Line Items]
Goodwill gross, beginning balance	$ 214,561	$ 215,169
Accumulated impairment loss, beginning balance	(50,003)	(50,003)
Goodwill net, beginning balance	164,558	165,166
Goodwill, Acquisition	107,048
Goodwill, Foreign currency translation adjustments	(44)	(608)
Goodwill gross, ending balance	321,565	214,561
Accumulated impairment loss, ending balance	(50,003)	(50,003)
Goodwill net, ending balance	271,562	164,558
Indefinite lived intangible asset, Ending balance	3,300
Trade Name [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Indefinite lived intangible asset, Beginning balance	3,305	3,443
Indefinite lived intangible asset, foreign currency translation adjustments	(7)	(138)
Indefinite lived intangible asset, Ending balance	3,298	3,305
U.S. [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Goodwill gross, beginning balance	150,461	150,461
Accumulated impairment loss, beginning balance
Goodwill net, beginning balance	150,461	150,461
Goodwill, Acquisition	105,004
Goodwill, Foreign currency translation adjustments
Goodwill gross, ending balance	255,465	150,461
Accumulated impairment loss, ending balance
Goodwill net, ending balance	255,465	150,461
U.S. [Member] | Trade Name [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Indefinite lived intangible asset, Beginning balance	200	200
Indefinite lived intangible asset, foreign currency translation adjustments
Indefinite lived intangible asset, Ending balance	200	200
U.K. [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Goodwill gross, beginning balance	63,393	63,994
Accumulated impairment loss, beginning balance	(50,003)	(50,003)
Goodwill net, beginning balance	13,390	13,991
Goodwill, Foreign currency translation adjustments	(29)	(601)
Goodwill gross, ending balance	63,364	63,393
Accumulated impairment loss, ending balance	(50,003)	(50,003)
Goodwill net, ending balance	13,361	13,390
U.K. [Member] | Trade Name [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Indefinite lived intangible asset, Beginning balance	3,105	3,243
Indefinite lived intangible asset, foreign currency translation adjustments	(7)	(138)
Indefinite lived intangible asset, Ending balance	3,098	3,105
Other International [Member]
Indefinite-lived Intangible Assets by Segment [Line Items]
Goodwill gross, beginning balance	707	714
Goodwill net, beginning balance	707	714
Goodwill, Acquisition	2,044
Goodwill, Foreign currency translation adjustments	(15)	(7)
Goodwill gross, ending balance	2,736	707
Goodwill net, ending balance	$ 2,736	$ 707