Concentrations of Credit Risk Percentage Receivables by State/Region (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Concentration Risk [Line Items]
Concentration risk	10.00%	10.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | California [Member]
Concentration Risk [Line Items]
Concentration risk	9.00%	9.10%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | Midwest (IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, WI) [Member]
Concentration Risk [Line Items]
Concentration risk	22.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | Southeast (AL, FL, GA, KY, MS, NC, SC, TN) [Member]
Concentration Risk [Line Items]
Concentration risk	21.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | West (AK, CO, HI, ID, MT, NV, OR, UT, WA, WY) [Member]
Concentration Risk [Line Items]
Concentration risk	8.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | Middle Atlantic (DE, DC,, MD, NJ, PA, VA, WV) [Member]
Concentration Risk [Line Items]
Concentration risk	19.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | Southwest (AZ, AR, LA, NM, OK, TX) [Member]
Concentration Risk [Line Items]
Concentration risk	8.00%
Geographic Concentration Risk [Member] | Accounts Receivable [Member] | Northeast (CT, ME, MA, NH, NY, RI, VT) [Member]
Concentration Risk [Line Items]
Concentration risk	13.00%