Convertible Debentures and Credit Arrangements - Credit Arrangements Narrative (Details) - Credit Arrangements [Member]	12 Months Ended
	Dec. 31, 2016 USD ($)
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 25,000,000.0
After Amendment [Member]
Line of Credit Facility [Line Items]
Maturity date	Dec. 19, 2016
Landlord Of Compu Com Systems Incs Dallas Headquarters [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 6,300,000
Letter of credit expiration date	Mar. 19, 2019