Stock Plans 6 (Details) - $ / shares		12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Weighted average estimated values and assumptions for employee stock option grants
Weighted average fair value (in dollars per share)		$ 4.72	$ 4.42	$ 4.68
Dividend yield		3.17%	3.56%	3.37%
Expected volatility factor	[1]	21.00%	22.00%	23.00%
Risk-free interest rate	[2]	2.10%	1.50%	1.90%
Expected life (in years)	[3]	6 years	6 years	6 years

[1] Expected volatility is measured using historical daily price changes of the Company’s stock over the respective expected term of the options and the implied volatility derived from the market prices of the Company’s traded options.

[2] The risk-free rate for periods within the contractual term of the stock options is based on the U.S. Treasury yield curve in effect at the time of grant.

[3] The expected life is the number of years the Company estimates that options will be outstanding prior to exercise. The Company’s computation of expected life was determined based on the simplified method (the average of the vesting period and option term).