Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Marketable securities, maturity in months, minimum	3 months
Marketable securities, maturity in months, maximum	12 months
Definite-lived intangible assets, useful life in years, minimum	1
Definite-lived intangible assets, useful life in years, maximum	20
Asset retirement obligations, useful life in years, minimum	1
Asset retirement obligations, useful life in years, maximum	25
Equipment and Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life in years, minimum	15
Property, plant and equipment, useful life in years, maximum	25
Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life in years, minimum	5
Property, plant and equipment, useful life in years, maximum	7