Consolidated Statements Of Stockholders' Equity - USD ($) $ in Millions	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance as of beginning-of-year at Dec. 31, 2017	$ 10,713	$ 4,405	$ 3,327
Cumulative effect from adoption of new accounting standards at Dec. 31, 2017		(644)	644
Stock compensation/issued for benefit plans	(1)
Net income (loss)		407		$ 407
Other comprehensive income (loss), net of tax			(1,614)	(1,614)
Balance as of end-of-period at Mar. 31, 2018	10,712	4,168	2,357	17,237
Balance as of beginning-of-year at Dec. 31, 2018	11,237	4,423	659	16,319
Stock compensation/issued for benefit plans	3
Net income (loss)		133		133
Dividends declared		(200)
Other comprehensive income (loss), net of tax			1,995	1,995
Balance as of end-of-period at Mar. 31, 2019	$ 11,240	$ 4,356	$ 2,654	$ 18,250