Variable Interest Entities New Markets Tax Credit (Details) (New Mexico Data Center, USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012
New Mexico Data Center
Related Party Transaction [Line Items]
Tax credit percentage of original investment amount	39.00%
Years in which tax credit to be claimed	7 years
Tax credit percent for each of the first three years	5.00%
Tax credit percent for each of the remaining four years	6.00%
Investment cannot be redeemed before the end of seven-year period	7 years
Principal amount loaned to the Investment Fund	$ 15.5
Proceeds loaned to related party	20.9
Capital contribution by Wells Fargo	5.9	5.9
Deferred finance costs capitalized	$ 1.2
Tax credit recapture percentage		100.00%
Tax credit recapture period		7 years