Stockholders' Equity (Details) - USD ($)		3 Months Ended		6 Months Ended
		Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		$ 69,000		$ 69,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, common stock, shares				8,994,968
Beginning balance				$ 394,408,000
Stock option exercises, amount				(1,583,000)
Stock-based compensation				1,535,000
Net income		$ 6,182,000	$ 9,341,000	17,935,000	$ 14,784,000
Other comprehensive loss	[1]			$ 604,000
Ending balance, common stock, shares		9,027,594		9,027,594
Ending balance		$ 412,968,000		$ 412,968,000
Pre-tax unrealized loss on available-for-sale investments				$ 983,000,000
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance, common stock, shares				8,994,968
Beginning balance				$ 90,000
Stock option exercises, shares				32,626
Stock option exercises, amount				$ 0
Stock-based compensation				0
Net income				0
Other comprehensive loss				$ 0
Ending balance, common stock, shares		9,027,594		9,027,594
Ending balance		$ 90,000		$ 90,000
Additional paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				244,791,000
Stock option exercises, amount				(1,583,000)
Stock-based compensation				1,535,000
Net income				0
Other comprehensive loss				0
Ending balance		244,743,000		244,743,000
Retained earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				148,141,000
Stock option exercises, amount
Stock-based compensation				0
Net income				17,935,000
Other comprehensive loss				0
Ending balance		166,145,000		166,145,000
Accumulated other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				1,386,000
Stock option exercises, amount				0
Stock-based compensation				0
Net income				0
Other comprehensive loss	[1]			604,000
Ending balance		$ 1,990,000		$ 1,990,000

[1] Other comprehensive income is comprised of unrealized gains and losses on available-for-sale investments. Unrealized gains before tax effect on available-for-sale securities were $983,000 for the six months ended September 30, 2017.