CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income	$ 183.6	$ 111.2	$ 280.3	$ 241.9
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $0.4, $0.3, $1.2 and $1.7, respectively	0.8	0.7	2.3	1.9
Settlement cost, net of tax of $0.0, $2.4, $3.2 and $2.4, respectively	0.0	3.8	5.0	3.8
Postretirement Benefit Plans:
Amortization of deferred net loss, net of tax of $0.0, $0.2, $0.0 and $0.6, respectively	0.0	0.3	0.0	0.9
Amortization of prior service cost, net of tax of ($0.2), ($0.3), ($0.7) and ($0.8), respectively	(0.4)	(0.4)	(1.2)	(1.3)
Other comprehensive income, net of tax	0.4	4.4	6.1	5.3
Comprehensive income	$ 184.0	$ 115.6	$ 286.4	$ 247.2