Summary of Significant Accounting Policies Concentration of Credit Risk (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Concentration Risk [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile, Percent	100.00%	100.00%	94.00%
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Europe, Percent			6.00%