Consolidated Statement of Shareholder's Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Beginning balance at Dec. 31, 2017	$ 1,871	$ 0	$ 161	$ (998)	$ 2,708
Net income	217				217
Other comprehensive loss	(11)			(11)
Ending balance at Jun. 30, 2018	2,077	0	161	(1,009)	2,925
Beginning balance at Mar. 31, 2018	2,010	0	161	(988)	2,837
Net income	88				88
Other comprehensive loss	(21)			(21)
Ending balance at Jun. 30, 2018	2,077	0	161	(1,009)	2,925
Beginning balance at Dec. 31, 2018	2,196	0	161	(1,060)	3,095
Net income	215				215
Other comprehensive loss	(15)			(15)
Ending balance at Jun. 30, 2019	2,396	0	161	(1,075)	3,310
Beginning balance at Mar. 31, 2019	2,306	0	161	(1,053)	3,198
Net income	112				112
Other comprehensive loss	(22)			(22)
Ending balance at Jun. 30, 2019	$ 2,396	$ 0	$ 161	$ (1,075)	$ 3,310