Subsequent Events (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jul. 26, 2018	Sep. 30, 2018
Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from sale of equity method investments	$ 55.0
MediaMath, Inc. | Subsequent Event [Member]
Subsequent Event [Line Items]
Equity Method Investments, Percent of Ownership Sold	39.13%
Proceeds from sale of equity method investments	$ 45.0
Equity Method Investments, Percent of Ownership Sold, Repurchase Option Within 180 Days	10.87%
Equity Method Investments, Sale Price, Repurchase Option Within 180 Days	$ 12.5
AdvantEdge Healthcare Solutions, Inc. | Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from sale of equity method investments	10.0
Equity Method Investments, Sale of Investments, Additional Amount Receivable After Certain Valuation Thresholds	$ 6.3
Scenario, Forecast | AdvantEdge Healthcare Solutions, Inc.
Subsequent Event [Line Items]
Equity Method Investment, Realized Gain (Loss) on Disposal		$ 5.5
Minimum | Scenario, Forecast | MediaMath, Inc.
Subsequent Event [Line Items]
Equity Method Investment, Realized Gain (Loss) on Disposal		43.0
Maximum | Scenario, Forecast | MediaMath, Inc.
Subsequent Event [Line Items]
Equity Method Investment, Realized Gain (Loss) on Disposal		$ 45.0