Investments - Summary of Investments in Debt Securities Outstanding (Details) (USD $) In Millions, unless otherwise specified	May 02, 2015
Cost
Less than one year	$ 0.7
Year two through year five	9.6
Year six through year ten	9.3
After ten years	0.1
Total investment in debt securities	19.7
Fair Value
Less than one year	0.7
Year two through year five	9.4
Year six through year ten	9.4
After ten years	0.1
Total investment in debt securities	$ 19.6