Share Repurchases (Details) - USD ($)			8 Months Ended	12 Months Ended
	Mar. 29, 2016	Jul. 28, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 29, 2016	May 31, 2015	May 14, 2015	Feb. 28, 2014
Share repurchase [Line Items]
Payments for Repurchase of Common Stock				$ 0	$ 75,000,000	$ 709,500,000
2014 Repurchase Program
Share repurchase [Line Items]
Authorized amount under our share repurchase program											$ 1,000,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount Terminated										$ 149,400,000
2015 Repurchase Program
Share repurchase [Line Items]
Payments for Repurchase of Common Stock			$ 75,000,000	$ 650,000,000
Authorized amount under our share repurchase program										$ 1,500,000,000
Repurchases of stock (in shares)				15,765,025		1,891,620
Stock Repurchase Program, Remaining Authorized Repurchase Amount				$ 850,000,000
2015 Repurchase Program | February 2016 Accelerated Share Repurchase
Share repurchase [Line Items]
Repurchases of stock (in shares)	2,766,558
Accelerated Share Repurchases Payment								$ 75,000,000
Accelerated Share Repurchases, Final Price Paid Per Share	$ 27.11
2015 Repurchase Program | May 2015 Accelerated Share Repurchase
Share repurchase [Line Items]
Repurchases of stock (in shares)		11,106,847
Accelerated Share Repurchases Payment									$ 500,000,000
Accelerated Share Repurchases, Final Price Paid Per Share		$ 45.02
Common Class A | 2014 Repurchase Program
Share repurchase [Line Items]
Repurchases of stock (in shares)							8,193,698
No Class Common Stock | 2014 Repurchase Program
Share repurchase [Line Items]
Payments for Repurchase of Common Stock						$ 123,300,000	$ 727,300,000
Repurchases of stock (in shares)						2,560,277	7,585,085