Capital Stock (Details 2) - Class A - Stock repurchase program - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Oct. 31, 2011
Stock repurchases
Amount of authorized stock repurchases approved for continuation under the current stock repurchase program			$ 150.0
Shares repurchased under the current stock repurchase program (in shares)	0	0
Approximate amount of repurchase authority remaining under the current stock repurchase program	$ 17.8