Changes to Significant Accounting Policies Narrative (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Change in Accounting Estimate [Line Items]
Property and equipment per unit value minimum	$ 1,000	$ 1,000
Property and equipment useful life minimum (in years)		1 year
Net Income [Member]
Change in Accounting Estimate [Line Items]
Change in accounting estimate, financial impact	9,000,000	19,700,000
Earnings Per Share, Basic [Member]
Change in Accounting Estimate [Line Items]
Change in accounting estimate, financial impact	$ 0.05	$ 0.11
Software and Hardware [Member]
Change in Accounting Estimate [Line Items]
Property and equipment useful life (in years)		4 years
Software and Hardware [Member] | Historical Useful Life [Member]
Change in Accounting Estimate [Line Items]
Property and equipment useful life (in years)		3 years