Financial Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis, Alternative [Abstract]
Fair Value of contingent consideration at December 31, 2015	$ 50	$ 59
Additions: contingent consideration completed during the period	19
Reduction: payment of contingent consideration	26
Fair Value of contingent consideration at December 31, 2016	(2)
Interest rate swap contracts | Fair Value Measurements Recurring Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps (included in other current and non-current liabilities)	33	47
Interest rate swap contracts | Fair Value Measurements Recurring Member | Level I
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps (included in other current and non-current liabilities)	0	0
Interest rate swap contracts | Fair Value Measurements Recurring Member | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps (included in other current and non-current liabilities)	33	47
Interest rate swap contracts | Fair Value Measurements Recurring Member | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps (included in other current and non-current liabilities)	0	0
Deferred Compensation Plan Assets [Member] | Fair Value Measurements Recurring Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (included in other non-current assets)	3	3
Deferred Compensation Plan Assets [Member] | Fair Value Measurements Recurring Member | Level I
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (included in other non-current assets)	3	3
Deferred Compensation Plan Assets [Member] | Fair Value Measurements Recurring Member | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (included in other non-current assets)	0	0
Deferred Compensation Plan Assets [Member] | Fair Value Measurements Recurring Member | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (included in other non-current assets)	0	0
Contingent Consideration for Acquisitions [Member] | Fair Value Measurements Recurring Member
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Liabilities, Fair Value Disclosure	50	59
Contingent Consideration for Acquisitions [Member] | Fair Value Measurements Recurring Member | Level I
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Liabilities, Fair Value Disclosure	0	0
Contingent Consideration for Acquisitions [Member] | Fair Value Measurements Recurring Member | Level II
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Liabilities, Fair Value Disclosure	0	0
Contingent Consideration for Acquisitions [Member] | Fair Value Measurements Recurring Member | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Liabilities, Fair Value Disclosure	$ 50	$ 59