Subsequent Events (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Subsequent Event [Line Items]
Restructuring Charges		$ 59	$ 127	$ 1,777	$ 2,156
Revenue from Contract with Customer, Including Assessed Tax		$ 205,304	$ 219,289	645,780	644,488
Life Sciences Drug Safety Practice [Member]
Subsequent Event [Line Items]
Revenue from Contract with Customer, Including Assessed Tax				1,900
Employee Severance [Member]
Subsequent Event [Line Items]
Restructuring Charges				$ 300	$ 200
Subsequent Event [Member] | Minimum
Subsequent Event [Line Items]
Restructuring Charges	$ 15,500
Subsequent Event [Member] | Maximum
Subsequent Event [Line Items]
Restructuring Charges	19,500
Subsequent Event [Member] | Employee Severance [Member] | Minimum
Subsequent Event [Line Items]
Restructuring Charges	3,500
Subsequent Event [Member] | Employee Severance [Member] | Maximum
Subsequent Event [Line Items]
Restructuring Charges	4,500
Subsequent Event [Member] | Office Space Reductions [Member] | Minimum
Subsequent Event [Line Items]
Restructuring Charges	12,000
Subsequent Event [Member] | Office Space Reductions [Member] | Maximum
Subsequent Event [Line Items]
Restructuring Charges	$ 15,000