Employee Stock Purchase Plan (Details) (Employee Stock Purchase Plan [Member])	6 Months Ended
Dec. 31, 2011 M	Jun. 30, 2011 M	Dec. 31, 2010 M	Jun. 30, 2010 M	Dec. 31, 2009 M	Jun. 30, 2009 M
Employee Stock Purchase Plan [Member]
Assumptions used in estimating the fair value
Expected volatility	45.86%	46.58%	47.44%	48.10%	48.83%	47.32%
Expected term	6	6	6	6	6	6
Risk-free interest rate	0.10%	0.19%	0.22%	0.20%	0.35%	0.27%
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.

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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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