Stock Options - Summary of the grant-date fair value of stock options granted (Details) (USD $)	12 Months Ended
Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Grant-date fair value		$ 5.69	$ 5.15
Volatility factor		85.92%	82.83%
Dividend yield
Risk-free interest rate		1.49%	2.07%
Expected term (in years)		7 years 91 days	7 years

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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