Stock Plans 5 (Details) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Summary of stock option information by exercise price range
Shares, Options outstanding | shares	4.3
Aggregate intrinsic value, Options outstanding | $	$ 19.1
Weighted average remaining contractual life, Options outstanding (in years)	7 years 1 month 6 days
Weighted average exercise price, Options outstanding (in dollars per share)	$ 29.48
Shares, Options exercisable | shares	2.4
Aggregate intrinsic value, Options exercisable | $	$ 14.6
Weighted average remaining contractual life, Options exercisable (in years)	5 years 10 months 24 days
Weighted average exercise price, Options exercisable (in dollars per share)	$ 27.79
Exercise Price Range $22.82 - $25.00
Summary of stock option information by exercise price range
Range of exercise prices, Minimum (in dollars per share)	22.82
Range of exercise prices, Maximum (in dollars per share)	$ 25.00
Shares, Options outstanding | shares	0.7
Aggregate intrinsic value, Options outstanding | $	$ 7.1
Weighted average remaining contractual life, Options outstanding (in years)	4 years 9 months 18 days
Weighted average exercise price, Options outstanding (in dollars per share)	$ 23.50
Shares, Options exercisable | shares	0.7
Aggregate intrinsic value, Options exercisable | $	$ 7.1
Weighted average remaining contractual life, Options exercisable (in years)	4 years 9 months 18 days
Weighted average exercise price, Options exercisable (in dollars per share)	$ 23.50
Exercise Price Range $25.01 - $30.00
Summary of stock option information by exercise price range
Range of exercise prices, Minimum (in dollars per share)	25.01
Range of exercise prices, Maximum (in dollars per share)	$ 30.00
Shares, Options outstanding | shares	0.8
Aggregate intrinsic value, Options outstanding | $	$ 4.6
Weighted average remaining contractual life, Options outstanding (in years)	5 years 8 months 12 days
Weighted average exercise price, Options outstanding (in dollars per share)	$ 27.85
Shares, Options exercisable | shares	0.7
Aggregate intrinsic value, Options exercisable | $	$ 4.5
Weighted average remaining contractual life, Options exercisable (in years)	5 years 7 months 6 days
Weighted average exercise price, Options exercisable (in dollars per share)	$ 27.81
Exercise Price Range $30.01 - over
Summary of stock option information by exercise price range
Range of exercise prices, Minimum (in dollars per share)	$ 30.01
Shares, Options outstanding | shares	2.8
Aggregate intrinsic value, Options outstanding | $	$ 7.4
Weighted average remaining contractual life, Options outstanding (in years)	8 years
Weighted average exercise price, Options outstanding (in dollars per share)	$ 31.34
Shares, Options exercisable | shares	1.0
Aggregate intrinsic value, Options exercisable | $	$ 3.0
Weighted average remaining contractual life, Options exercisable (in years)	6 years 10 months 24 days
Weighted average exercise price, Options exercisable (in dollars per share)	$ 30.82