Debt Debt - Schedule of Maturities of Long-Term Debt (Details) $ in Millions	Mar. 31, 2018 USD ($)
Other Commitments [Line Items]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 48
Long-term Debt, Maturities, Repayments of Principal in Year Two	64
Long-term Debt, Maturities, Repayments of Principal in Year Three	64
Long-term Debt, Maturities, Repayments of Principal in Year Four	64
Long-term Debt, Maturities, Repayments of Principal in Year Five	64
Long-term Debt, Maturities, Repayments of Principal after Year Five	8,715
Long-term debt, Maturities, Repayments of Principal, Total	9,019
Contractual Obligation, Future Minimum Payments Due, Remainder of Fiscal Year	428
Contractual Obligation, Due in Second Year	534
Contractual Obligation, Due in Third Year	544
Contractual Obligation, Due in Fourth Year	544
Contractual Obligation, Due in Fifth Year	544
Contractual Obligation, Due after Fifth Year	9,725
Contractual Obligation	12,319
Interest Expense [Member]
Other Commitments [Line Items]
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	380
Other Commitment, Due in Second Year	470
Other Commitment, Due in Third Year	480
Other Commitment, Due in Fourth Year	480
Other Commitment, Due in Fifth Year	480
Other Commitment, Due after Fifth Year	1,010
Other Commitment	$ 3,300