Investments - Summary of Investments in Debt Securities Outstanding (Details) $ in Millions	Jul. 30, 2016 USD ($)
Cost
Less than one year	$ 4.5
Year two through year five	11.7
Year six through year ten	7.3
After ten years	0.0
Total investment in debt securities	23.5
Fair Value
Less than one year	4.0
Year two through year five	11.8
Year six through year ten	7.6
After ten years	0.0
Total investment in debt securities	$ 23.4