Consolidated Statement of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net change in unrealized gains on available-for-sale securities, net tax benefit	$ 0.0	$ 0.0	$ 0.0	$ (0.1)
Net unrealized gains on cash flow hedges, net tax provision	17.6	(30.1)	69.9	49.8
Postretirement plans and workers' compensation obligations, net tax provision	$ 2.1	$ 1.8	$ 6.3	$ 11.2