Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 28, 2015	Jul. 27, 2015	Apr. 30, 2013
Subsequent events
Stock Repurchase Program, Authorized Amount			$ 90
Subsequent event
Subsequent events
Stock Repurchase Program, Authorized Amount		$ 100
Subsequent event | Class A
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.17
Subsequent event | Class A | Maximum
Subsequent events
Stock Repurchase Program, Authorized Amount		$ 100
Subsequent event | Class B
Subsequent events
Quarterly dividend declared (in dollars per share)	$ 0.17