Restructuring Charges (Summary of Restructuring Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Centralization Of Global Sales And Marketing Structure
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	$ 11,512
Accruals	10,700	$ 12,000
Payments	12,665
Balance at the end of the period	9,547	11,512
Cumulative Charges Incurred	22,726
Workforce Reduction Plan
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	0
Accruals	27,953
Payments	23,696
Balance at the end of the period	4,257	0
Cumulative Charges Incurred	27,953
Termination benefits | Centralization Of Global Sales And Marketing Structure
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	8,389
Accruals	2,711
Payments	3,192
Balance at the end of the period	7,908	8,389
Cumulative Charges Incurred	11,591
Termination benefits | Workforce Reduction Plan
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	0
Accruals	27,953
Payments	23,696
Balance at the end of the period	4,257	0
Cumulative Charges Incurred	27,953
Contract termination costs | Centralization Of Global Sales And Marketing Structure
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	338
Accruals	0
Payments	0
Balance at the end of the period	338	338
Cumulative Charges Incurred	338
Other related costs | Centralization Of Global Sales And Marketing Structure
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	2,785
Accruals	7,989
Payments	9,473
Balance at the end of the period	1,301	$ 2,785
Cumulative Charges Incurred	$ 10,797