Revenue Revenue (Details)	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	100.00%	100.00%
Functional Verification, including Emulation and Prototyping Hardware
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	26.00%	23.00%
Digital IC Design and Signoff
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	30.00%	29.00%
Custom IC Design
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	26.00%	26.00%
System Interconnect and Analysis
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	9.00%	10.00%
IP
Revenue from External Customer [Line Items]
Percentage of product and maintenance revenue by product group	9.00%	12.00%