Annual report pursuant to Section 13 and 15(d)

Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Cash Flows (Details)

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Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Cash Flows (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Condensed Cash Flow Statements, Captions [Line Items]      
Cash used in operating activities $ 977 $ 0 $ (171)
Cash flows from investing activities      
Property, plant and equipment, net (1,290) (2,315) (2,913)
Net cash provided by (used in) investing activities (1,290) (2,353) (2,975)
Cash flows from financing activities      
Repayments of debt (2,173) (5,251) 0
Debt issuance and deferred financing costs (50) (115) (170)
Distributions to owners (294) (99) (99)
Net cash provided by financing activities 1,297 2,524 2,591
Net increase (decrease) in cash, cash equivalents and restricted cash 984 171 (555)
Cash, cash equivalents and restricted cash—beginning of period 605 434 989
Cash, cash equivalents and restricted cash—end of period 1,589 605 434
Parent Company [Member]      
Condensed Cash Flow Statements, Captions [Line Items]      
Cash used in operating activities (101) (53) (43)
Cash flows from investing activities      
Property, plant and equipment, net 0 0 (1)
Investments in subsidiaries (245) (2,429) 13
Distributions received from affiliates, net 1,431 218 18
Net cash provided by (used in) investing activities 1,186 (2,211) 30
Cash flows from financing activities      
Proceeds from issuance of debt 1,500 2,560 0
Repayments of debt (1,470) 0 0
Debt issuance and deferred financing costs (22) (73) 0
Distributions to owners (294) (99) (99)
Net cash provided by financing activities (286) 2,388 (99)
Net increase (decrease) in cash, cash equivalents and restricted cash 799 124 (112)
Cash, cash equivalents and restricted cash—beginning of period 234 110 222
Cash, cash equivalents and restricted cash—end of period $ 1,033 $ 234 $ 110