Description of Business (Details)	Dec. 31, 2012 Customers
Description of Business [Line Items]
Number of customers	5,400,000
Government Contracts [Member]
Description of Business [Line Items]
Number of customers	2,900,000
Government Contracts [Member] | U.S. Department of Veterans Affairs [Member]
Description of Business [Line Items]
Number of customers	14,000
Number of states in which entity operates	7