Supplemental Guarantor Financial Information (Condensed Consolidating Statements Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenues	$ 174,182		$ 165,059		$ 147,294		$ 138,041		$ 134,749		$ 136,605		$ 132,948		$ 127,776		$ 624,576		$ 532,078		$ 493,353
Operating costs and expenses																	547,301		465,815		450,353
Operating (loss) income																	77,275		66,263		43,000
Interest (income) expense, net, including amortization of deferred financing costs and bond discounts																	21,109		28,658		32,528
Write-off of deferred financing costs and bond discounts																			7,296
Redemption costs for early extinguishment of debt																			7,193
Other (income) expense, net																	(804)		(878)		456
Income (loss) before income taxes																	56,970		23,994		10,016
Income tax (benefit) expense																	(13,176)		(17,139)		4,245
Net income (loss)	8,046	[1]	46,800	[1]	8,742	[1]	6,558	[1]	8,000	[2]	20,655	[2]	8,248	[2]	4,230	[2]	70,146	[1]	41,133	[2]	5,771
Net income (loss) attributable to noncontrolling interests																	(87)		174		494
Net income attributable to controlling interests and available to common stockholders	8,153	[1]	46,885	[1]	8,715	[1]	6,480	[1]	8,028	[2]	20,763	[2]	8,203	[2]	3,965	[2]	70,233	[1]	40,959	[2]	5,277
Parent [Member]
Operating costs and expenses																	9,604		6,329		4,967
Operating (loss) income																	(9,604)		(6,329)		(4,967)
Interest (income) expense, net, including amortization of deferred financing costs and bond discounts																	(940)		5,473		3,868
Write-off of deferred financing costs and bond discounts																			7,296
Redemption costs for early extinguishment of debt																			7,193
Equity in (earnings) losses of subsidiaries																	(47,421)		(30,014)		(18,646)
Other (income) expense, net																	(19,252)		(20,921)		(93)
Income (loss) before income taxes																	58,009		24,644		9,904
Income tax (benefit) expense																	(12,116)		(16,468)		4,154
Net income (loss)																	70,125		41,112		5,750
Net income attributable to controlling interests and available to common stockholders																	70,125		41,112		5,750
Guarantors [Member]
Revenues																	505,716		426,180		404,076
Operating costs and expenses																	417,762		354,236		358,972
Operating (loss) income																	87,954		71,944		45,104
Interest (income) expense, net, including amortization of deferred financing costs and bond discounts																	18,084		18,125		23,025
Equity in (earnings) losses of subsidiaries																	7,572		6,734		5,254
Other (income) expense, net																	15,714		18,098		(905)
Income (loss) before income taxes																	46,584		28,987		17,730
Income tax (benefit) expense																	(1,060)		(671)		91
Net income (loss)																	47,644		29,658		17,639
Net income attributable to controlling interests and available to common stockholders																	47,644		29,658		17,639
Non-Guarantors [Member]
Revenues																	123,248		108,969		91,419
Operating costs and expenses																	124,344		108,342		88,577
Operating (loss) income																	(1,096)		627		2,842
Interest (income) expense, net, including amortization of deferred financing costs and bond discounts																	3,965		5,060		5,635
Other (income) expense, net																	2,734		1,945		1,454
Income (loss) before income taxes																	(7,795)		(6,378)		(4,247)
Net income (loss)																	(7,795)		(6,378)		(4,247)
Net income attributable to controlling interests and available to common stockholders																	(7,795)		(6,378)		(4,247)
Elimination [Member]
Revenues																	(4,388)		(3,071)		(2,142)
Operating costs and expenses																	(4,409)		(3,092)		(2,163)
Operating (loss) income																	21		21		21
Equity in (earnings) losses of subsidiaries																	39,849		23,280		13,392
Income (loss) before income taxes																	(39,828)		(23,259)		(13,371)
Net income (loss)																	(39,828)		(23,259)		(13,371)
Net income (loss) attributable to noncontrolling interests																	(87)		174		494
Net income attributable to controlling interests and available to common stockholders																	$ (39,741)		$ (23,433)		$ (13,865)

[1] Includes $37.0 million of tax benefit recorded in the quarter ended September 30 as a result of a tax reporting change with respect to the Company's U.K. operations.

[2] Includes release of $23.7 million and $3.5 million in previously-recognized valuation allowances related to the Company's United States segment for the quarters ended September 30 and December 31, respectively. Additionally, the quarter ended September 30 includes pre-tax charges of approximately $14.5 million related to certain charges associated with the refinancing of the Company's outstanding debt obligations.