Credit Facilities (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Credit Facilities (Textual) [Abstract]
Maximum borrowing capacity under the bank line of credit facility	$ 10.0
Amounts outstanding under the bank line of credit facility	0
Borrowings under the bank line of credit facility	$ 0
Line of credit facility financial covenant terms	maintain unrestricted cash, cash equivalents and short-term investments to current liabilities of atleast 1.75 to 1.00
Interest rate	3.25%
Unrestricted cash cash equivalents and short-term investments to current liabilities ratio	3.61 to 1
Annualized rate of LIBOR	0.24%
Percentage added to LIBOR to facilitate line of credit	1.75%