Stockholders' Equity Stock Split (Details) $ / shares in Units, $ in Millions		3 Months Ended	9 Months Ended
	Aug. 18, 2016	Jul. 31, 2016 USD ($)	Jan. 31, 2017 USD ($) $ / shares shares	Apr. 30, 2016 $ / shares shares
Class of Stock [Line Items]
Stockholders' Equity Note, Stock Split, Conversion Ratio	2
Adjustments to Additional Paid in Capital, Stock Split | $			$ 0
Common Stock, Par or Stated Value Per Share | $ / shares			$ 0.15
Common stock, Class A, voting [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized			170,000,000	85,000,000
Common Stock, Shares, Issued			170,000,000	85,000,000
Common Stock, Par or Stated Value Per Share | $ / shares			$ 0.15	$ 0.15
Common stock, Class B, nonvoting [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized			400,000,000	400,000,000
Common Stock, Shares, Issued			284,626,000	142,313,000
Common Stock, Par or Stated Value Per Share | $ / shares			$ 0.15	$ 0.15
Additional Paid-in Capital [Member]
Class of Stock [Line Items]
Adjustments to Additional Paid in Capital, Stock Split | $		$ 34	$ 34