Summary of Significant Accounting Policies (Details 4)	12 Months Ended
	Dec. 31, 2012
Buildings
Property and equipment
Estimated useful lives	20 years
Assets held under capital leases | Minimum
Property and equipment
Estimated useful lives	1 year
Assets held under capital leases | Maximum
Property and equipment
Estimated useful lives	15 years
Leasehold improvements | Minimum
Property and equipment
Estimated useful lives	1 year
Leasehold improvements | Maximum
Property and equipment
Estimated useful lives	15 years
Furniture and equipment | Minimum
Property and equipment
Estimated useful lives	3 years
Furniture and equipment | Maximum
Property and equipment
Estimated useful lives	7 years