Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) plan	Dec. 31, 2017 USD ($) plan	Dec. 31, 2016 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Multiemployer plan, contributions by employer	$ 158,000,000	$ 132,000,000	$ 140,000,000
Health care cost trend rate assumed next fiscal year	6.50%
Health care cost trend rate	4.68%
Defined contribution plan, employer matching contribution	5.00%
Defined contribution plan, employers matching contribution for vesting plan	4.00%
Defined contribution plans, cost	$ 137,000,000	71,000,000
Defined contribution plan, assets and liabilities	233,000,000	278,000,000
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension assets or obligations, threshold, per plan	20,000,000
Curtailment / settlement loss (gain)	2,000,000	(45,000,000)	(26,000,000)
Expected amortization of gain (loss), next fiscal year	(15,000,000)
Expected amortization of prior service cost (credit), next fiscal year	1,000,000
Fair values of the plan assets	1,866,000,000	2,059,000,000	567,000,000
Employer contributions	51,000,000	50,000,000
Estimated future employer contributions in next fiscal year	22,000,000
Pension plan | Fixed income and cash investment funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair values of the plan assets	937,000,000	658,000,000
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Curtailment / settlement loss (gain)	(5,000,000)	2,000,000	(2,000,000)
Expected amortization of gain (loss), next fiscal year	7,000,000
Expected amortization of prior service cost (credit), next fiscal year	(3,000,000)
Fair values of the plan assets	0	0	$ 0
Employer contributions	21,000,000	$ 13,000,000
Estimated future employer contributions in next fiscal year	$ 19,000,000
U.K.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of retirement plans | plan		2
U.S. | Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of retirement plans | plan	4
Foreign | Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of retirement plans | plan	6
Fair value measured at Net Asset Value per share
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair values of the plan assets	$ 1,802,000,000	$ 1,684,000,000
Fair value measured at Net Asset Value per share | Equity securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of plan assets valued using NAV	30.00%	30.00%
Fair value measured at Net Asset Value per share | Fixed income and cash investment funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of plan assets valued using NAV	48.00%	28.00%
Fair value measured at Net Asset Value per share | Alternative investments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percent of plan assets valued using NAV	19.00%	24.00%
Fair Value, Inputs, Level 1, 2 and 3 | Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair values of the plan assets	$ 64,000,000	$ 375,000,000
Level 3 | Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair values of the plan assets	$ 0	$ 86,000,000