Special Charges and Credits (Details) (USD $)	3 Months Ended			24 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2012 January 25, 2012 Secondary Offering [Member]	Dec. 31, 2012 January 25, 2012 Secondary Offering [Member]	Jan. 25, 2012 January 25, 2012 Secondary Offering [Member]
Restructuring Cost and Reserve [Line Items]
Shares sold by certain stockholders in secondary offering (in shares)					12,650,000
Payments of stock issuance costs			$ 200,000	$ 1,300,000
Stock issuance cost reimbursements			300,000	600,000
Special charges (credits)	$ 23,000	$ (72,000)