Stockholders' Equity - Summary of Noncontrolling Interest Balances By Projects (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Noncontrolling interest	$ 1,040	$ 1,112	$ 1,045	$ 1,254
Logan's Gap
Noncontrolling Interest [Line Items]
Noncontrolling interest	123	132
Panhandle 1
Noncontrolling Interest [Line Items]
Noncontrolling interest	118	131
Panhandle 2
Noncontrolling Interest [Line Items]
Noncontrolling interest	162	176
Post Rock
Noncontrolling Interest [Line Items]
Noncontrolling interest	101	116
Amazon Wind
Noncontrolling Interest [Line Items]
Noncontrolling interest	92	101
Broadview Project
Noncontrolling Interest [Line Items]
Noncontrolling interest	243	257
Futtsu
Noncontrolling Interest [Line Items]
Noncontrolling interest	9	10
Meikle
Noncontrolling Interest [Line Items]
Noncontrolling interest	44	57
MSM
Noncontrolling Interest [Line Items]
Noncontrolling interest	38	37
Stillwater
Noncontrolling Interest [Line Items]
Noncontrolling interest	92	95
Belle River
Noncontrolling Interest [Line Items]
Noncontrolling interest	$ 18	$ 0