Unaudited Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Unaudited Condensed Consolidated Statements Of Income And Comprehensive Income
Tax effect on unrealized capital gains (losses) on securities-available-for-sale	$ (11.4)	$ 20.0	$ (44.9)	$ 27.2
Reclassification adjustment for net capital gains included in net income, tax effect	1.7	(0.3)	1.2	(1.1)
Other Comprehensive Income Loss Reclassification Adjustment From AOCI On Derivatives Tax	(7.0)	0.0	1.8	0.0
Prior service credit and net losses arising during the period, tax effect	0.0	0.0	0.0	(0.3)
Reclassification adjustment for amortization to net periodic pension cost, tax effect	$ 1.2	$ 0.2	$ 3.5	$ 0.7