Revenue Recognition (Schedule of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 26, 2021	Mar. 27, 2020	Mar. 26, 2021	Mar. 27, 2020
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 319,558	$ 351,815	$ 709,432	$ 643,692
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	$ 153,267	$ 186,586	$ 254,341	$ 294,213
Revenue from contract with customer, percent	48.00%	53.00%	36.00%	46.00%
International
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 166,291	$ 165,229	$ 455,091	$ 349,479
Revenue from contract with customer, percent	52.00%	47.00%	64.00%	54.00%
Licensing
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 303,585	$ 328,865	$ 676,590	$ 586,548
Revenue from contract with customer, licensing percent	100.00%	100.00%	100.00%	100.00%
Revenue from contract with customer, percent	95.00%	93.00%	95.00%	91.00%
Products and services
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 15,973	$ 22,950	$ 32,842	$ 57,144
Revenue from contract with customer, percent	5.00%	7.00%	5.00%	9.00%
Broadcast
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 104,813	$ 128,677	$ 244,113	$ 230,810
Revenue from contract with customer, licensing percent	35.00%	39.00%	36.00%	39.00%
PC
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 51,104	$ 45,791	$ 83,839	$ 77,634
Revenue from contract with customer, licensing percent	17.00%	14.00%	12.00%	13.00%
Mobile
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 65,673	$ 75,697	$ 171,296	$ 110,178
Revenue from contract with customer, licensing percent	22.00%	23.00%	25.00%	19.00%
CE
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 48,284	$ 49,199	$ 100,205	$ 98,044
Revenue from contract with customer, licensing percent	16.00%	15.00%	15.00%	17.00%
Other
Revenue from External Customer [Line Items]
Revenue from contract with customer	$ 33,711	$ 29,501	$ 77,137	$ 69,882
Revenue from contract with customer, licensing percent	10.00%	9.00%	12.00%	12.00%