Restructuring Charges - Narrative (Details) € in Millions, $ in Millions		6 Months Ended
	Jan. 24, 2017 position	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Payments for restructuring			$ 71
ITALY
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		€ 241		$ 275
Payments for restructuring		209	239
UNITED KINGDOM
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		79		90
Payments for restructuring		69	79
Restructuring and related cost, expected number of positions eliminated | position	500
Employee-related costs | ITALY
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		179		204
Employee-related costs | UNITED KINGDOM
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		59		67
Asset impairment costs
Restructuring Cost and Reserve [Line Items]
Payments for restructuring			0
Asset impairment costs | ITALY
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		25		29
Asset impairment costs | UNITED KINGDOM
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		11		13
Other exit costs
Restructuring Cost and Reserve [Line Items]
Payments for restructuring			$ 7
Other exit costs | ITALY
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		37		42
Other exit costs | UNITED KINGDOM
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected cost		€ 10		$ 11