Short-Term Investments (Details)			3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2012 Minimum [Member]
Investment [Line Items]
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	9	7