CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net income	$ 111.2	$ 187.3	$ 241.9	$ 337.4
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $0.3, $0.3, $1.7 and $0.9, respectively	0.7	0.5	1.9	1.4
Settlement cost, net of tax of $2.4, $0.0, $2.4 and $0.0, respectively	3.8	0.0	3.8	0.0
Postretirement Benefit Plans:
Amortization of deferred net loss, net of tax of $0.2, $0.1, $0.6 and $0.4, respectively	0.3	0.1	0.9	0.6
Amortization of prior service cost, net of tax of ($0.3), ($0.2), ($0.8) and ($0.8), respectively	(0.4)	(0.4)	(1.3)	(1.3)
Amortization of deferred interest rate swap hedging losses, net of tax of $0.0, $0.0, $0.0 and $0.1, respectively	0.0	0.1	0.0	0.2
Other comprehensive income, net of tax	4.4	0.3	5.3	0.9
Comprehensive income	$ 115.6	$ 187.6	$ 247.2	$ 338.3