Short-Term Investments (Details)			9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2011 Minimum [Member]
Short-term investment securities, maturity date			90 days
Remaining months for contractual maturities of short-term investments, minimum	1	1
Remaining months for contractual maturities of short-term investments, maximum	10	6