Employee Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	$ 213
Defined Benefit Plan, Accumulated Benefit Obligation	466	$ 213
Defined Benefit Plan, Benefit Obligation	(488)	(232)	$ (207)
Defined Benefit Plan, Plan Assets, Amount	332	107	87
Defined Benefit Plan, Plan Assets, Benefits Paid	(4)
Defined Benefit Plan, Acquired and Established Plan Changes, Plan Assets	213	16
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	156	125
Defined Benefit Plan, Acquired and Established Plan Changes, Plan Assets	216	23
Defined Benefit Plan, Service Cost	15	14
Defined Benefit Plan, Interest Cost	5	4
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	0	(1)
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	11	(2)
pension benefit obligation, benefits paid	(10)	(10)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	19	(3)
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)	7	(2)
Defined Benefit Plan, Plan Assets, Contributions by Employer	13	14
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant	2	2
defined benefit plan, plan assets, actuarial gain loss	(20)	0
Defined Benefit Plan, Benefit Obligation, Benefits Paid	(10)	(10)
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)	$ 19	0
Executive Retirement Plan Discount Rate	0.40%
Expense related to matching contributions	$ 98	87	$ 79
Executive Retirement Plan Rate of Compensation Increase	3.40%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	0.40%
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (3)
Executive retirement plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	50	47
Defined Benefit Plan, Benefit Obligation	(54)	(50)
Defined Benefit Plan, Plan Assets, Amount	0	0
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	54	50
International retirement plans [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	204	166
Defined Benefit Plan, Benefit Obligation	(223)	(182)
Defined Benefit Plan, Plan Assets, Amount	123	107
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	100	75
U.K. Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation	212
Defined Benefit Plan, Benefit Obligation	(212)
Defined Benefit Plan, Plan Assets, Amount	209
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position	3
Fair Value, Inputs, Level 3 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Accumulated Benefit Obligation		213
Defined Benefit Plan, Plan Assets, Amount	207	$ 0
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)	(20)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)	19
Fair Value, Inputs, Level 2 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Fair Value, Inputs, Level 1 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1
Other Contract [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	207
Other Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	207
Other Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Other Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Defined Benefit Plan, Cash [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1
Defined Benefit Plan, Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Defined Benefit Plan, Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	0
Defined Benefit Plan, Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Plan Assets, Amount	1
BTG Acquisition [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Benefit Obligation	$ (216)
International retirement plans [Member] | Maximum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate		2.34%
Defined Benefit Plan, Plan Assets, Assumptions used to Determine Expected Return		4.10%
Executive Retirement Plan Rate of Compensation Increase		6.78%
International retirement plans [Member] | Minimum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate		0.50%
Defined Benefit Plan, Plan Assets, Assumptions used to Determine Expected Return		1.90%
Executive Retirement Plan Rate of Compensation Increase		1.50%
Other International Plans [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate	0.75%
Defined Benefit Plan, Plan Assets, Assumptions used to Determine Expected Return	2.05%
Executive Retirement Plan Rate of Compensation Increase	2.65%
Domestic Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate	2.94%
Executive Retirement Plan Rate of Compensation Increase	1.50%	3.00%
Domestic Plan [Member] | Maximum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate		4.25%
Domestic Plan [Member] | Minimum [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate		4.00%
U.K. Plan [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Executive Retirement Plan Discount Rate	0.60%
Defined Benefit Plan, Plan Assets, Assumptions used to Determine Expected Return	0.60%
Executive Retirement Plan Rate of Compensation Increase	3.00%