CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income	$ 87.5	$ 100.8	$ 130.7	$ 150.1
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $0.6, $0.3, $1.4 and $0.6, respectively	0.8	0.5	1.2	0.9
Postretirement Benefit Plans:
Amortization of deferred net loss, net of tax of $0.2, $0.2, $0.4 and $0.3, respectively	0.4	0.3	0.6	0.5
Amortization of prior service cost, net of tax of ($0.2), ($0.3), ($0.5) and ($0.6), respectively	(0.5)	(0.5)	(0.9)	(0.9)
Amortization of deferred interest rate swap hedging losses, net of tax of $0.0, $0.0, $0.0 and $0.1, respectively	0.0	0.0	0.0	0.1
Other comprehensive income, net of tax	0.7	0.3	0.9	0.6
Comprehensive income	$ 88.2	$ 101.1	$ 131.6	$ 150.7