Segment Information (Reconciliation Of Adjusted Earnings Before Interest, Taxes, Depreciation And Amortization To Net Income Attributable To Controlling Interests) (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Adjusted EBITDA	$ 64,853,000		$ 53,936,000		$ 121,733,000		$ 102,462,000
Loss (gain) on disposal of assets	316,000		157,000		584,000		360,000
Other expense (income)	(5,261,000)	[1]	(2,050,000)	[1]	(5,230,000)	[1]	(2,471,000)	[1]
Noncontrolling interests	(391,000)		(536,000)		(764,000)		(955,000)
Stock-based compensation expense	3,692,000	[2]	2,568,000	[2]	6,903,000	[2]	5,725,000	[2]
Acquisition-related expenses	7,642,000		1,184,000		10,729,000		4,006,000
Other adjustment to selling, general, and administrative expenses							446,000	[3]
EBITDA	58,855,000		52,613,000		109,511,000		95,351,000
Interest expense, net, including amortization of deferred financing costs and note discount, and redemption cost for early extinguishment of debt	8,789,000		5,290,000		17,544,000		10,585,000
Income tax expense (benefit)	8,015,000		10,034,000		13,788,000		16,014,000
Depreciation and accretion expense	19,597,000		15,881,000		37,943,000		32,166,000
Amortization of intangible assets	8,465,000		6,081,000		16,682,000		11,829,000
Net income attributable to controlling interests and available to common stockholders	13,989,000		15,327,000		23,554,000		24,757,000
Non-recurring insurance settlement gain					$ 4,800,000
Mexico [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	49.00%				49.00%

[1] 2014 amounts include non-recurring settlement gain of $4.8 million.

[2] Amounts exclude 49% of the expenses incurred by the Company’s Mexico subsidiary as such amounts are allocable to the noncontrolling interest stockholders.

[3] Adjustment relates to severance-related costs associated with the management of the Company’s U.K. operations.