Consolidated Statements Of Stockholders' Equity - USD ($) $ in Millions	Common Stock	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance as of beginning-of-year at Dec. 31, 2014	$ 6,622	$ 6,022	$ 3,096
Stock compensation/issued for benefit plans	74
Net income (loss)		871		$ 871
Retirement of common stock/cancellation of shares	(316)	(384)
Common stock dividends declared		(151)
Other comprehensive income (loss), net of tax			(1,433)	(1,433)
Balance as of end-of-period at Sep. 30, 2015	6,380	6,358	1,663	14,401
Balance as of beginning-of-year at Dec. 31, 2015	6,298	6,474	845	13,617
Stock compensation/issued for benefit plans	26
Net income (loss)		999		999
Retirement of common stock/cancellation of shares	(415)	(260)
Common stock dividends declared		(176)
Other comprehensive income (loss), net of tax			2,532	2,532
Balance as of end-of-period at Sep. 30, 2016	$ 5,909	$ 7,037	$ 3,377	$ 16,323