Marketable Securities - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 28, 2018	Oct. 29, 2017	Oct. 28, 2018	Oct. 29, 2017
Investments, Debt and Equity Securities [Abstract]
Other-than-temporary impairment losses	$ 0	$ 0	$ 0	$ 0