Retirement Plans (Retirement Plans, Funded Status) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]      
Expense for the defined contribution plans for continuing operations $ 193 $ 173 $ 111
Foreign Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Assets for Plan Benefits, Defined Benefit Plan 39 2  
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at end of period 951 1,200  
Fair value of plan assets at end of period 832 940  
Funded status at end of period 119 280  
Amounts recognized on the Consolidated Balance Sheets      
Accrued employee compensation and benefits 8 15  
Employee compensation and benefits 150 267  
Pension plans in which projected benefit obligation exceeded plan assets      
Projected benefit obligation (a) [1] 176 1,202  
Fair value of plan assets 18 920  
Pension plans in which accumulated benefit obligation exceeded plan assets      
Accumulated benefit obligation (a) [1] 105 1,139  
Fair value of plan assets 18 920  
Defined Benefit Plan, Accumulated Benefit Obligation 878 1,200  
Foreign Plan [Member] | Cash and Cash Equivalents [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 12 11  
Foreign Plan [Member] | Equity funds (b)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[3] 137 204  
Foreign Plan [Member] | Bond funds (c)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[4] 323 369  
Foreign Plan [Member] | alternatives fund [Domain]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[5] 209 184  
Foreign Plan [Member] | Real Estate Funds [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[6] 109 126  
Foreign Plan [Member] | Other assets      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 42 46  
Foreign Plan [Member] | Level 1      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 6 7  
Foreign Plan [Member] | Level 1 | Cash and Cash Equivalents [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 0 0  
Foreign Plan [Member] | Level 1 | Equity funds (b)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[3] 0 0  
Foreign Plan [Member] | Level 1 | Bond funds (c)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[4] 0 0  
Foreign Plan [Member] | Level 1 | alternatives fund [Domain]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[5] 0 0  
Foreign Plan [Member] | Level 1 | Real Estate Funds [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[6] 0 0  
Foreign Plan [Member] | Level 1 | Other assets      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 6 7  
Foreign Plan [Member] | Level 2      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 762 842  
Foreign Plan [Member] | Level 2 | Cash and Cash Equivalents [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 12 11  
Foreign Plan [Member] | Level 2 | Equity funds (b)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[3] 137 204  
Foreign Plan [Member] | Level 2 | Bond funds (c)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[4] 302 323  
Foreign Plan [Member] | Level 2 | alternatives fund [Domain]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[5] 209 184  
Foreign Plan [Member] | Level 2 | Real Estate Funds [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[6] 81 98  
Foreign Plan [Member] | Level 2 | Other assets      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 21 22  
Foreign Plan [Member] | Level 3      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 64 91  
Foreign Plan [Member] | Level 3 | Cash and Cash Equivalents [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period 0 0  
Foreign Plan [Member] | Level 3 | Equity funds (b)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[3] 0 0  
Foreign Plan [Member] | Level 3 | Bond funds (c)      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[4] 21 46  
Foreign Plan [Member] | Level 3 | alternatives fund [Domain]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[5] 0 0  
Foreign Plan [Member] | Level 3 | Real Estate Funds [Member]      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period [2],[6] 28 28  
Foreign Plan [Member] | Level 3 | Other assets      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Fair value of plan assets at end of period $ 15 $ 17  
United Kingdom Pension Plan [Member]      
Pension plans in which accumulated benefit obligation exceeded plan assets      
United Kingdom pension plan percentage of international pension plans' projected benefit obligations 80.00%    
[1] Our United Kingdom pension plan was underfunded as of December 31, 2017 and overfunded as of December 31, 2018. As such, the fair value of plan assets and projected and accumulated benefit obligation related to this plan are no longer captured in this table at December 31, 2018.
[2] Common/collective trust funds are valued at the net asset value of units held by the plans at year-end.
[3] Strategy is to invest in diversified funds of global common stocks.
[4] Strategy is to invest in diversified funds of fixed income securities of varying geographies and credit quality and whose cash flows approximate the maturities of the benefit obligation.
[5] Strategy is to invest in a fund of diversifying investments, including but not limited to reinsurance, commodities and currencies.
[6] Strategy is to invest in diversified funds of real estate investment trusts and private real estate.