Acquisitions (Estimated Fair Value Of The Assets Acquired And Liabilities Assumed) (Details) (Maverick [Member], USD $)	3 Months Ended
	Mar. 31, 2012
Business Acquisition [Line Items]
Current Assets	$ 17,046,000
Property and Equipment	92,856,000
Other Intangible Assets	29,400,000	[1]
Goodwill	58,477,000	[2]
Other Non-Current Assets	464,000
Total Assets Acquired	198,243,000
Current Liabilities	9,854,000
Deferred Income Taxes
Total Liabilities Assumed	9,854,000
Net Assets Acquired	188,389,000
Customer Relationships [Member]
Business Acquisition [Line Items]
Other intangible assets, amortizable	25,300,000
Other intangible assets, amortization period, years	15
Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Other intangible assets, amortizable	3,600,000
Other intangible assets, amortization period, years	5
Intellectual Property [Member]
Business Acquisition [Line Items]
Other intangible assets, amortizable	380,000
Other intangible assets, amortization period, years	15
Trade Name [Member]
Business Acquisition [Line Items]
Other intangible assets, indefinite life	$ 170,000

[1] Other intangible assets consists of customer relationship of $25.3 million, amortizable over 15 years, non-compete agreements of $3.6 million, amortizable over five years, intellectual property of $380,000, amortizable over 15 years, and trade name of $170,000 with an indefinite life.

[2] Goodwill is primarily attributable to operational and cost synergies expected to be realized from the acquisition by integrating Maverick's equipment and assembled workforce. All of the goodwill is expected to be deductible for tax purposes.