Credit Facilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Credit Facility [Line Items]
Proceeds from bank borrowings	$ 0	$ 6,900,000	$ 4,600,000
Amount outstanding	0	2,000,000
Credit facility | Silicon Valley Bank
Credit Facility [Line Items]
Borrowing capacity	30,000,000
Proceeds from bank borrowings	20,000,000
Borrowing base requirement	40,000,000
Period for borrowing base requirement	90 days
Cash and cash equivalents, net of amount outstanding under credit agreement	20,000,000
Interest rate over prime	1.00%
Available borrowing capacity	30,000,000
Credit facility | Silicon Valley Bank | Prime Rate [Member]
Credit Facility [Line Items]
Interest rate over prime	4.00%
Letters of credit | Silicon Valley Bank
Credit Facility [Line Items]
Letters of credit outstanding	0
Amount outstanding	$ 0
Threshold One [Member]
Credit Facility [Line Items]
Customer accounts receivable concentration limit	25.00%
Threshold Two [Member]
Credit Facility [Line Items]
Customer accounts receivable concentration limit	50.00%
Threshold Three [Member]
Credit Facility [Line Items]
Customer accounts receivable concentration limit	85.00%