Common Stock (Tables)

12 Months Ended

Dec. 31, 2017

Common Stock.

Summary of the cost and number of Class A common stock repurchased

	Year Ended December 31,
	2017			2016
	Number of shares	Cost of shares		Number of shares	Cost of shares
	repurchased	repurchased		repurchased	repurchased
	(amounts in millions, except share amount)
Stock repurchase programs:
July 27, 2015	277,886		18.2	501,229		26.8
Total	277,886	$	18.2	501,229	$	26.8