Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Member's Equity	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ 43,009	$ 42,778	$ 231
Cash distributions	(1,100)	(1,100)
Comprehensive income (loss), net of tax	1,146	1,145	1
Balance at Mar. 31, 2018	43,052	42,795	257
Balance at Dec. 31, 2017	43,009	42,778	231
Cash distributions	(4,150)		0
Comprehensive income (loss), net of tax	3,847
Balance at Sep. 30, 2018	42,703	42,447	256
Balance at Mar. 31, 2018	43,052	42,795	257
Cash distributions	(1,175)	(1,175)	0
Comprehensive income (loss), net of tax	1,309	1,309	0
Balance at Jun. 30, 2018	43,186	42,929	257
Cash distributions	(1,875)	(1,875)	0
Comprehensive income (loss), net of tax	1,392	1,393	(1)
Balance at Sep. 30, 2018	42,703	42,447	256
Balance at Dec. 31, 2018	42,649	42,519	130
Cash distributions	(1,200)	(1,200)	0
Comprehensive income (loss), net of tax	1,315	1,253	62
Balance at Mar. 31, 2019	42,764	42,572	192
Balance at Dec. 31, 2018	42,649	42,519	130
Cash distributions	(3,400)
Comprehensive income (loss), net of tax	4,119
Balance at Sep. 30, 2019	43,368	43,176	192
Balance at Mar. 31, 2019	42,764	42,572	192
Cash distributions	(1,200)	(1,200)	0
Comprehensive income (loss), net of tax	1,338	1,338	0
Balance at Jun. 30, 2019	42,902	42,710	192
Cash distributions	(1,000)	(1,000)	0
Comprehensive income (loss), net of tax	1,466	1,466	0
Balance at Sep. 30, 2019	$ 43,368	$ 43,176	$ 192