Stock-Based Compensation - Reconciliation of Outstanding Stock Options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 29, 2018 USD ($) $ / shares shares
Shares Under Option
Outstanding (in shares) | shares	404,301
Granted (in shares) | shares	78,721
IXYS converted awards (in shares) | shares	499,027
Exercised (in shares) | shares	(296,914)
Forfeited (in shares) | shares	(15,779)
Outstanding (in shares) | shares	669,356
Exercisable (in shares) | shares	420,422
Weighted Average Price
Outstanding (in dollars per share) | $ / shares	$ 110.04
Granted (in dollars per share) | $ / shares	192.59
IXYS converted awards (in dollars per share) | $ / shares	92.52
Exercised (in dollars per share) | $ / shares	87.85
Forfeited (in dollars per share) | $ / shares	120.59
Outstanding (in dollars per share) | $ / shares	116.29
Exercisable (in dollars per share) | $ / shares	$ 100.14
Weighted Average Remaining Contract Life and Aggregate Intrinsic Value
Outstanding (Years)	5 years 4 months 24 days
Outstanding | $	$ 36,494
Exercisable (Years)	4 years 9 months 18 days
Exercisable | $	$ 28,542