Earnings per Share ("EPS") Share Repurchase Program (Details) - USD ($) shares in Millions	1 Months Ended		3 Months Ended	48 Months Ended
	Jul. 31, 2015	May. 07, 2015	Jun. 30, 2015	Dec. 31, 2018	Feb. 28, 2015
Accelerated Share Repurchases [Line Items]
Treasury Stock, Shares, Acquired			0.7
Class A and Class B common stock [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchase program, amount authorized					$ 1,000,000,000.0
Stock Repurchase Program, Period in Force				4 years
Class B common stock [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchased during period, amount		$ 50,000,000
Class B common stock [Member] | Subsequent Event [Member]
Accelerated Share Repurchases [Line Items]
Stock repurchased during period, amount	$ 50,000,000