Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2011 M
Cash Equivalents
Maximum maturity of cash equivalents (in months)	3
Computers
Land, Buildings and Improvements
Useful life, minimum (in years)	3
Useful life, maximum (in years)	5
Equipment
Land, Buildings and Improvements
Useful life, minimum (in years)	7
Useful life, maximum (in years)	10
Buildings
Land, Buildings and Improvements
Useful life, minimum (in years)	35
Useful life, maximum (in years)	40
Building improvements
Land, Buildings and Improvements
Useful life, minimum (in years)	10
Useful life, maximum (in years)	20