Summary of Significant Accounting Policies - Useful Lives for Major Categories of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2011 years
Land Improvements
Property, Plant and Equipment [Line Items]
Property Plant and Equipment useful life (in years)	50
Buildings
Property, Plant and Equipment [Line Items]
Property Plant and Equipment minimum useful life (in years)	28
Property Plant and Equipment maximum useful life (in years)	40
Furniture Fixtures Equipment And Purchased Software [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment minimum useful life (in years)	3
Property Plant and Equipment maximum useful life (in years)	5