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	68
Net income (loss)		644		$ 644
Retirement of common stock/cancellation of shares	(221)	(279)
Common stock dividends declared		(101)
Other comprehensive income (loss), net of tax			(1,152)	(1,152)
Balance as of end-of-period at Jun. 30, 2015	6,469	6,286	1,944	14,699
Balance as of beginning-of-year at Dec. 31, 2015	6,298	6,474	845	13,617
Stock compensation/issued for benefit plans	14
Net income (loss)		533		533
Retirement of common stock/cancellation of shares	(303)	(172)
Common stock dividends declared		(119)
Other comprehensive income (loss), net of tax			2,350	2,350
Balance as of end-of-period at Jun. 30, 2016	$ 6,009	$ 6,716	$ 3,195	$ 15,920