Debt Revolver (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) extension	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Other Long-term Debt, Noncurrent	$ 5,536,000,000	$ 5,536,000,000
Line of Credit Facility, Expiration Date	May 28, 2022
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,400,000,000
Line of Credit Facility, Maximum Borrowing Capacity	$ 0
Line of Credit Facility, Number of One Year Extensions | extension	2
Line of Credit, Period of Extension Options	1 year
Line of Credit Facility, Remaining Borrowing Capacity	$ 107,000,000
Bridge Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500,000,000
Maximum [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital	0.65
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Ratio of Indebtedness to Net Capital	0.31