Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Net income	$ 191.6	$ 114.2	$ 240.8	$ 121.2
Other comprehensive income
Foreign currency translation gain (loss)	0.2	0.0	(0.1)	0.0
Defined benefit pension and postretirement plans:
Net loss arising from remeasurement during the period, net of tax of $0.6	1.1	0.0	1.1	0.0
Amortization of prior service benefits, net of tax of ($1.4), ($1.4), ($2.8), ($2.8)	(2.4)	(2.4)	(4.8)	(4.8)
Amortization of net actuarial loss, net of tax of $3.8, $1.8, $6.2, $4.2	6.9	3.0	11.0	7.2
Reclassification adjustment for curtailment loss included in net income, net of tax of $0.1	0.2	0.0	0.2	0.0
Other comprehensive income	6.0	0.6	7.4	2.4
Total comprehensive income	$ 197.6	$ 114.8	$ 248.2	$ 123.6