General General (Details) - USD ($)		1 Months Ended			3 Months Ended	9 Months Ended		12 Months Ended
	May 15, 2018	Jul. 26, 2018	May 31, 2018	May 31, 2017	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Apr. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Cash and cash equivalents					$ 44,522,000	$ 44,522,000				$ 20,751,000
Marketable securities					25,100,000	25,100,000
Cash, cash equivalents, and marketable securities					69,600,000	69,600,000
Proceeds from sale of equity method investments		$ 55,000,000
Severance costs					1,000,000	3,800,000
Cash and cash equivalents					44,522,000	44,522,000				20,751,000
Long-term restricted cash equivalents					0	0				6,336,000
Total cash, cash equivalents and restricted cash equivalents					44,522,000	44,522,000	$ 40,653,000			$ 27,087,000	$ 28,394,000
Proceeds from credit facility						35,000,000	$ 50,000,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Liquidity threshold				$ 20,000,000
Minimum aggregate appraised value plus liquidity threshold				350,000,000
Scenario, Forecast
Debt Instrument [Line Items]
Severance costs								$ 4,000,000
Scenario, Forecast | Minimum
Debt Instrument [Line Items]
Projected annual cost savings								8,000,000
Scenario, Forecast | Maximum
Debt Instrument [Line Items]
Projected annual cost savings								$ 9,000,000
MediaMath, Inc.
Debt Instrument [Line Items]
Percent of ownership sold		39.13%
Proceeds from sale of equity method investments		$ 45,000,000
Percent of ownership sold, repurchase option within 180 days		10.87%
Repurchase option within 180 days		$ 12,500,000
AdvantEdge Healthcare Solutions, Inc.
Debt Instrument [Line Items]
Proceeds from sale of equity method investments		10,000,000
Additional amount receivable after certain valuation thresholds		$ 6,300,000
Amended Credit Facility
Debt Instrument [Line Items]
Current borrowing capacity					15,000,000	15,000,000
Maximum borrowing capacity			$ 100,000,000.0
Cash and cash equivalent threshold			50,000,000		50,000,000	50,000,000
Long-term line of credit outstanding					$ 85,000,000	$ 85,000,000
Liquidity threshold			20,000,000
Minimum aggregate appraised value plus liquidity threshold			350,000,000
Deployment threshold			40,000,000.0
Expense threshold			11,500,000.0
Amended Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity			15,000,000.0
Amended Credit Facility | Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity			85,000,000.0
Long-term line of credit outstanding			35,000,000						$ 50,000,000
Proceeds from credit facility			$ 32,700,000
Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity				75,000,000.0
Long-term line of credit outstanding				50,000,000
Proceeds from credit facility				$ 44,300,000
2018 Debentures
Debt Instrument [Line Items]
Repayments of debt	$ 41,000,000