Employee Benefit Plans (Details Textual) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Benefits [Member]
Employee Benefit Plans (Textual) [Abstract]
Other postretirement benefit costs	$ 4.0	$ 4.0	$ 12.0	$ 11.0
Pension Benefits [Member] | UNS Gas and UNS Electric [Member]
Employee Benefit Plans (Textual) [Abstract]
Pension benefit costs	0.5	0.5	1.0	1.0
Other Postretirement Benefits [Member]
Employee Benefit Plans (Textual) [Abstract]
Other postretirement benefit costs	2.0	1.0	4.0	4.0
Other Postretirement Benefits [Member] | UNS Gas and UNS Electric [Member]
Employee Benefit Plans (Textual) [Abstract]
Other postretirement benefit costs	$ 0.1	$ 0.1	$ 0.1	$ 0.1