Acquisitions and Dispositions - Additional Information (Details) - USD ($)			3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 18, 2018	Jul. 22, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 17, 2018
Acquisitions And Dispositions [Line Items]
Proceeds from disposition					$ 0	$ 77,100,000
Gain (loss) on sale of business					(2,800,000)	53,500,000
Discontinued Operations, Disposed of by Sale | Language Solutions
Acquisitions And Dispositions [Line Items]
Proceeds from disposition		$ 77,500,000
Other Operating Income | Discontinued Operations, Disposed of by Sale | Language Solutions
Acquisitions And Dispositions [Line Items]
Gain (loss) on sale of business					(2,800,000)		$ 53,800,000
eBrevia
Acquisitions And Dispositions [Line Items]
Percentage of investment held in prior to acquisition								12.80%
Business consideration including contingent consideration							23,300,000
Payments to acquire business, net of cash acquired							200,000
Payable for initial consideration of business acquisition excluding contingent consideration and amount held in escrow	$ 1,800,000						1,800,000
Fair value of investment held in prior to acquisition	3,300,000						3,300,000
Maximum additional contingent consideration	3,500,000
Estimated fair value of contingent consideration	800,000		$ 800,000		800,000
Acquisition related expenses			$ 100,000	$ 0	$ 100,000	$ 500,000
Tax deductible goodwill	$ 0
eBrevia | Investment and Other Income
Acquisitions And Dispositions [Line Items]
Recognition of gain in previously held investment							$ 1,800,000