Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Unrealized losses arising during the period, tax expense (benefit)	$ 0.0	$ (0.1)	$ 0.2	$ 0.3
Reclassification adjustments for losses included in net income, tax benefit	1.0	1.9	3.1	3.9
Amortization of net actuarial losses, tax benefit	$ 0.5	$ 0.1	$ 1.0	$ 0.2