Investments - Summary of Investments in Debt Securities Outstanding (Details) $ in Millions	Aug. 01, 2015 USD ($)
Cost
Less than one year	$ 1.5
Year two through year five	10.6
Year six through year ten	7.9
After ten years	0.1
Total investment in debt securities	20.1
Fair Value
Less than one year	1.5
Year two through year five	10.3
Year six through year ten	7.8
After ten years	0.1
Total investment in debt securities	$ 19.7