Accumulated Other Comprehensive Income (Loss) - Reclassification Out of AOCI By Component (Details) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning			$ 645,372,000
Other comprehensive income (loss) before reclassifications			(2,698,000)
Net current-period other comprehensive income (loss)			(2,698,000)
Balance, ending	$ 647,558,000		647,558,000
Interest income and other, net	2,437,000	$ 1,948,000	4,108,000	$ 4,930,000
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning			(4,763,000)
Balance, ending	(7,461,000)		(7,461,000)
Cumulative translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning			(2,151,000)
Other comprehensive income (loss) before reclassifications			(2,999,000)
Net current-period other comprehensive income (loss)			(2,999,000)
Balance, ending	(5,150,000)		(5,150,000)
Unrealized gain (loss) on available-for-sale investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning			(2,677,000)
Other comprehensive income (loss) before reclassifications			301,000
Net current-period other comprehensive income (loss)			301,000
Balance, ending	(2,376,000)		(2,376,000)
Unrealized gain (loss) on available-for-sale investments | Reclassification out of accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Interest income and other, net			0
Pension adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, beginning			65,000
Other comprehensive income (loss) before reclassifications			0
Net current-period other comprehensive income (loss)			0
Balance, ending	$ 65,000		$ 65,000