CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net income	$ 104.8	$ 71.5	$ 140.8	$ 96.7
Pension Plan and Restoration of Retirement Income Plan:
Amortization of deferred net loss, net of tax of $0.4, $0.4, $0.8 and $0.8, respectively	0.8	0.7	1.4	1.5
Settlement cost, net of tax of $0.0, $3.2, $0.0 and $3.2, respectively	0.0	5.0	0.0	5.0
Postretirement Benefit Plans:
Amortization of prior service cost, net of tax of ($0.0), ($0.3), ($0.0) and ($0.5), respectively	0.0	(0.4)	0.0	(0.8)
Other comprehensive income, net of tax	0.8	5.3	1.4	5.7
Comprehensive income	$ 105.6	$ 76.8	$ 142.2	$ 102.4