Share-Based Compensation (Details)	12 Months Ended
Mar. 31, 2012 Y	Mar. 31, 2011 Y	Mar. 31, 2010 Y
Fair value of share-based payments
Expected volatility	33.00%	35.00%	35.00%
Risk-free interest rate %	0.50%	0.60%	2.00%
Expected term (in years)	3	3	4
Dividend yield

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

+ References+ Details

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.

+ References+ Details