Credit Facility and Accrued Interest Expense (Details) (Revolving working capital credit facility, USD $) In Thousands, unless otherwise specified	1 Months Ended					0 Months Ended			0 Months Ended	1 Months Ended
	Feb. 28, 2011	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 07, 2010	Jul. 30, 2013 Subsequent event	Feb. 07, 2010 Minimum	Feb. 28, 2011 Minimum	Mar. 08, 2012 Prime rate	Feb. 28, 2011 Prime rate
Credit facility and accrued interest expense
Maximum borrowing capacity				$ 25,000	$ 7,000
Ratio of current assets to current liabilities (excluding deferred revenue)							1.25
Variable base rate									prime rate	prime rate
Interest rate (as a percent)									0.50%	1.00%
Fee for unused portion (as a percent)	0.20%
Average principal amount of borrowings per quarter for which no fee charged								10,000
Borrowing base as a percentage of eligible accounts receivable				80.00%
Amount outstanding		6,000	6,000
Repayments of principal borrowings and accrued, but unpaid interest expenses						$ 6,033