Description of Business and Summary of Significant Accounting Policies - Accounts Receivables and Allowances (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 37,203,000		$ 37,203,000		$ 31,133,000
Deferred revenue included in accounts receivables	7,700,000		7,700,000
Allowance for Loan and Lease Losses, Provision for Loss, Gross	100,000	410,000	416,000	747,000
Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	28,100,000		28,100,000
Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 9,100,000		$ 9,100,000
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delivery Term for Contractual Elements of Revenue Arrangements			18 months