Condensed Consolidated Statements of Comprehensive Income Parentheticals (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Tax provision on change in unrealized (loss) gain on available-for-sale securities	$ (3.8)	$ (22.1)
Tax provision on reclassification adjustment for realized net gains on available-for-sale securities included in net income	0	60.3
Tax provision on change in unrealized (losses) gains on cash flow hedges	(0.3)	(0.6)
Tax provision (benefit) on reclassification adjustment for realized losses (gains) included in net income	$ 0.1	$ (0.1)