Investments - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2011
Schedule of Cost-method Investments [Line Items]
Impairment loss on investment in unconsolidated affiliate		$ 2,170,000	$ 20,696,000	$ 1,078,000
Investment in unconsolidated affiliate, loss		2,170,000	20,696,000
Other investments	$ 1,312,000	1,312,000	3,482,000
Equity in loss of unconsolidated affiliate			3,422,000	2,076,000
Mindjet
Schedule of Cost-method Investments [Line Items]
Impairment loss on investment in unconsolidated affiliate			$ 20,700,000	$ 1,100,000
Conversion ratio (number of shares)			0.2
Voting interest percentage			19.30%
Other investments	$ 2,300,000	$ 2,300,000	$ 2,300,000
Klablab
Schedule of Cost-method Investments [Line Items]
Ownership					51.00%
Noncontrolling interest					49.00%
Equity Securities | Mindjet
Schedule of Cost-method Investments [Line Items]
Voting interest percentage	19.30%	19.30%	19.30%
Other investments	$ 1,312,000	$ 1,312,000	$ 1,312,000
Investment	0	$ 0	$ 0
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Abandonment | Klablab
Schedule of Cost-method Investments [Line Items]
Loss on abandonment	$ 2,000,000