CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE OPERATIONS (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Income	$ 163.4	$ 77.5	$ 271.7	$ 180.5
Related to marketable securities:
Unrealized holding gains (losses) arising during the period	5.6	(1.8)	9.9	(0.1)
Reclassification adjustment for gains included in net income	(1.8)	(1.2)	(4.3)	(2.7)
Income tax effect	(1.4)	1.2	(2.1)	1.0
Marketable securities, net of tax	2.4	(1.8)	3.5	(1.8)
Related to employee benefit plans:
Prior service cost arising during period	9.9	27.5	29.6	40.2
Income tax effect	(3.7)	(10.3)	(11.1)	(15.1)
Employee benefit plans, net of tax	6.2	17.2	18.5	25.1
Related to interest rate derivative instruments:
Unrealized holding gains arising during the period	(2.1)	(18.3)	(5.3)	(19.4)
Income tax effect	0.7	6.9	(0.3)	7.3
Interest rate derivative instruments, net of tax	(1.4)	(11.4)	(5.6)	(12.1)
Other comprehensive income	7.2	4.0	16.4	11.2
Comprehensive income	$ 170.6	$ 81.5	$ 288.1	$ 191.7