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Accounting for Share-Based Compensation 3 (Details) (USD $)	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Stock Purchase Plan, Fair Value Assumptions
Weighted average fair value	$ 9.09	$ 6.00
Dividend yield	3.96%	0.91%
Expected volatility factor	59.00%	33.00%
Risk-free interest rate	0.80%	1.70%
Expected life (in years)	4 years 6 months	4 years 6 months

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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