Debt (Details) - USD ($)	Apr. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2014
Debt Instrument [Line Items]
Fair value adjustment related to hedged fixed rate debt		$ 3,000,000	$ 3,000,000
Long-term debt		1,895,000,000	1,850,000,000
Short-term borrowings		118,000,000	106,000,000
Total debt		$ 2,013,000,000	$ 1,956,000,000
Senior Notes 3.2 Percent Due October 1, 2026
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		3.20%	3.20%
Long-term debt		$ 497,000,000	$ 496,000,000
Senior Notes 4.625 Percent Due November 1, 2020
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		4.625%	4.625%
Aggregate principal Amount				$ 400,000,000
Long-term debt		$ 398,000,000	$ 398,000,000
Senior Notes 1.8 Percent Due September 25, 2017
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		1.80%	1.80%
Aggregate principal Amount		$ 300,000,000
Long-term debt		$ 300,000,000	$ 299,000,000
Senior Notes 6.625 Percent Due April 15, 2037
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		6.625%	6.625%
Long-term debt		$ 253,000,000	$ 254,000,000
Senior Notes 6.0 Percent Due April 15, 2017
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		6.00%	6.00%
Long-term debt		$ 200,000,000	$ 200,000,000
Senior Notes 5.62 Percent Due March 25, 2020
Debt Instrument [Line Items]
Debt, interest rate (as a percent)		5.62%	5.62%
Long-term debt		$ 200,000,000	$ 200,000,000
Revolving Credit Agreement
Debt Instrument [Line Items]
Aggregate principal Amount	$ 200,000,000
Long-term debt		$ 44,000,000