Pension Benefits (Details) - USD ($)	3 Months Ended					6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017		Mar. 31, 2017	Jun. 30, 2018		Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits						$ 5,000,000		$ 12,000,000
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 5,000,000		$ 4,000,000			11,000,000		8,000,000
UNITED STATES | General and Administrative Expense [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,000,000		3,000,000			4,000,000		6,000,000
UNITED STATES | Other pension (income) expense [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	9,000,000		10,000,000			18,000,000		20,000,000
Expected return on plan assets	(11,000,000)		(11,000,000)			(21,000,000)		(23,000,000)
Amortization of net loss	3,000,000		1,000,000			7,000,000		3,000,000
Amortization of prior service cost	2,000,000		1,000,000			3,000,000		2,000,000
Additional loss (gain) recognized due to settlements			(3,000,000)					(8,000,000)
Pension data adjustment	$ 0	[1]	$ 0	[1]	$ 22,000,000	$ 0	[1]	$ 22,000,000	[1]

[1] Reflects a non-cash, out-of-year charge related to the adjustment of certain historical deferred vested liability balances in the Plan during the first quarter of 2017 recorded in Other pension (income) expense. See Note 5.