Condensed Consolidated Statements of Comprehensive Income Parentheticals (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Tax provision on change in unrealized gains on available-for-sale securities	$ 6.1	$ 3.9	$ 28.2	$ 4.0
Tax provision on reclassification adjustment for realized net gains on available-for-sale securities included in net income	0.1	0.1	60.4	0.2
Tax provision (benefit) on change in unrealized gains (losses) on cash flow hedges	0.7	(1.6)	1.3	(1.6)
Tax provision on reclassification adjustment for realized gains included in net income	$ 0.4	$ 0.1	$ 0.3	$ 0.2