Revenue Recognition (Schedule of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 27, 2020	Mar. 29, 2019	Mar. 27, 2020	Mar. 29, 2019
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 351,815	$ 338,258	$ 643,692	$ 640,634
Revenue from contract with customer, percent	100.00%	100.00%	100.00%	100.00%
United States
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 186,586	$ 158,000	$ 294,213	$ 277,799
Revenue from contract with customer, percent	53.00%	47.00%	46.00%	43.00%
International
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 165,229	$ 180,258	$ 349,479	$ 362,835
Revenue from contract with customer, percent	47.00%	53.00%	54.00%	57.00%
Licensing
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 328,865	$ 310,308	$ 586,548	$ 570,587
Revenue from contract with customer, licensing percent	100.00%	100.00%	100.00%	100.00%
Revenue from contract with customer, percent	93.00%	92.00%	91.00%	89.00%
Products and services
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 22,950	$ 27,950	$ 57,144	$ 70,047
Revenue from contract with customer, percent	7.00%	8.00%	9.00%	11.00%
Broadcast
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 128,677	$ 122,424	$ 230,810	$ 222,562
Revenue from contract with customer, licensing percent	39.00%	39.00%	39.00%	39.00%
PC
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 45,791	$ 41,193	$ 77,634	$ 64,350
Revenue from contract with customer, licensing percent	14.00%	13.00%	13.00%	11.00%
Mobile
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 75,697	$ 66,759	$ 110,178	$ 100,932
Revenue from contract with customer, licensing percent	23.00%	22.00%	19.00%	18.00%
CE
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 49,199	$ 44,776	$ 98,044	$ 88,526
Revenue from contract with customer, licensing percent	15.00%	14.00%	17.00%	16.00%
Other
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 29,501	$ 35,156	$ 69,882	$ 94,217
Revenue from contract with customer, licensing percent	9.00%	12.00%	12.00%	16.00%