Stock-Based Compensation Plans (Tables)

6 Months Ended

Sep. 29, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]

The fair values of stock purchase plan rights granted in the second quarter of fiscal years 2019 and 2018 were estimated using the Black-Scholes option pricing model at the date of grant using the following assumptions:

	2019		2018
Expected life of options (years)	1.25		1.25
Expected stock price volatility	0.29		0.28
Risk-free interest rate	2.5	%	1.3	%
Dividend yield	2.0	%	2.2	%

Stock-Based compensation expense

The following table summarizes stock-based compensation expense related to stock awards granted under the Company’s equity incentive plans and rights to acquire stock granted under the Company’s Employee Stock Purchase Plan (ESPP):

	Three Months Ended				Six Months Ended
(In thousands)	September 29, 2018		September 30, 2017		September 29, 2018		September 30, 2017
Stock-based compensation included in:
Cost of revenues	$	2,249	$	2,147	$	4,284	$	4,297
Research and development	20,047		20,096		40,977		37,562
Selling, general and administrative	12,649		14,129		25,292		26,549
	$	34,945	$	36,372	$	70,553	$	68,408

Schedule of Share-based compensation, restricted stock units, valuation assumption [Table Text Block]

The per share weighted-average fair value of RSUs granted during the second quarter of fiscal 2019 was $62.79 ($59.99 for the second quarter of fiscal 2018), and for the first six months of fiscal 2019 was $63.00 ($59.89 for the first six months of fiscal 2018), which were calculated based on estimates at the date of grant using the following weighted-average assumptions:

	Three Months Ended				Six Months Ended
	September 29, 2018		September 30, 2017		September 29, 2018		September 30, 2017
Risk-free interest rate	2.7	%	1.7	%	2.7	%	1.7	%
Dividend yield	2.2	%	2.2	%	2.2	%	2.2	%

Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of restricted stock unit activity and related information

A summary of the Company’s RSU activity and related information is as follows:

	RSUs Outstanding
(Shares in thousands)	Number of Shares		Weighted-Average Grant-Date Fair Value Per Share
April 1, 2017	6,988		$	42.93
Granted	3,718		$	60.18
Vested	(3,016	)	$	43.30
Cancelled	(701	)	$	48.16
March 31, 2018	6,989		$	51.39
Granted	2,964		$	63.00
Vested	(2,293	)	$	48.60
Cancelled	(251	)	$	52.20
September 29, 2018	7,409