Significant Accounting Policies (Narrative) (Details) $ in Thousands		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) distributor	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies [Line Items]
Lease losses related to consolidation of leased assets		$ 0	$ 0	$ (187)
Operating lease right-of-use assets	$ 194,500	206,154
Operating lease liabilities	256,400	256,407
Adjustment to retained earnings	$ 800	838	132,778	388
Allowance for doubtful accounts		$ 6,200	$ 3,600
Estimated useful lives of intangible assets		6 years 29 days	6 years 1 month 20 days
Amortization of capitalized contract costs		$ 44,800	$ 38,100
Short-term contract acquisition cost		50,400	41,000
Long-term contract acquisition cost		81,000	68,200
Asset impairment charges related to contract assets		0	0
Amount capitalized related to internal use software		3,400	14,800
Amount expensed related to internal use software		19,700	25,900	27,300
Capitalized costs for internally developed software to be sold as a service		10,600	7,300
Amount expensed related to internally developed computer software to be sold as a service		13,000	14,400	18,500
Advertising costs		90,400	99,100	85,600
Pension Plan | Foreign Plan
Significant Accounting Policies [Line Items]
Termination indemnities		12,500	11,200
Termination indemnities, compensation expense		$ 1,600	1,800	$ 2,600
Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		3 years
Licensing agreement term		1 year
Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		7 years
Licensing agreement term		5 years
Contract-based intangible assets | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		3 years
Contract-based intangible assets | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		5 years
Internal use software | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		3 years
Internal use software | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		7 years
Internally developed software to be sold as a service
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		2 years
Patents | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		7 years
Patents | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of intangible assets		10 years
As Previously Reported
Significant Accounting Policies [Line Items]
Lease losses related to consolidation of leased assets			42,200
Deferred rent liability			$ 20,500
Arrow Group | Customer concentration risk | Accounts receivable
Significant Accounting Policies [Line Items]
Number of major distributors | distributor		1
Concentration risk percentage		14.00%	17.00%