Condensed Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Tax benefit (provision) on change in unrealized gains on available-for-sale securities	$ 0.4	$ 0.6	$ (0.3)	$ 0.7
Tax provision on reclassification adjustment for realized net gains on available-for-sale securities included in net income	0.0	0.5	0.0	0.5
Tax provision on change in unrealized gains on cash flow hedges	(0.8)	(0.1)	(2.5)	(0.6)
Tax provision on reclassification adjustment for realized net (gains) losses included in net income	$ 0.6	$ 0.3	$ 0.9	$ 0.1