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Stockholders' Equity (Details) (USD $)	12 Months Ended
Stockholders' Equity (Details) (USD $)	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Weighted-average assumptions for options issued during the indicated periods
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	58.80%	62.80%	50.50%
Risk-free interest rate	1.90%	2.10%	1.80%
Expected life of options (in years)	3.8	4.3	4.5
Weighted-average grant-date fair value	$ 19.17	$ 12.60	$ 6.32

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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