Consolidated Condensed Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Consolidated Condensed Statements of Comprehensive Income (Unaudited) [Abstract]
Tax benefit of change in postretirement benefit plans	$ 0	$ 11.9	$ 0	$ 23.7
Tax expense of net change in unrealized gains on investment securities	0	2.9	0	6.6
Tax benefit of amortization of prior service costs	0	0.2	0	0.5
Tax benefit of amortization of net actuarial loss	0	11.7	0	23.2
Tax (expense) benefit of amortization of net actuarial loss	0	0	0	0
Tax benefit of unrealized losses arising during period	0	0.2	0	0.5
Tax expense of gains realized during the period	$ 0	$ 2.7	$ 0	$ 6.1