Employee Benefit Plans - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets contributions by employer	$ 5
Additional estimated contributions by employer during fiscal year	17
Total estimated contributions by employer during fiscal year	28
Postretirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets contributions by employer	0
Additional estimated contributions by employer during fiscal year	1
Total estimated contributions by employer during fiscal year	2
Postemployment Retirement Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Plan assets contributions by employer	8
Additional estimated contributions by employer during fiscal year	8
Total estimated contributions by employer during fiscal year	$ 30