Description of Business and Summary of Significant Accounting Policies - Accounts Receivables and Allowances (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 33,096,000		$ 33,096,000		$ 31,133,000
Deferred revenue included in accounts receivables	7,300,000		7,300,000
Allowance for Loan and Lease Losses, Provision for Loss, Gross	50,000	326,000	316,000	337,000
Billed Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	25,400,000		25,400,000
Unbilled Revenues [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 7,700,000		$ 7,700,000
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delivery Term for Contractual Elements of Revenue Arrangements			18 months