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	27
Net income (loss)		300		$ 300
Retirement of common stock/cancellation of shares	(156)	(194)
Common stock dividends declared		(51)
Other comprehensive income (loss), net of tax			557	557
Balance as of end-of-period at Mar. 31, 2015	6,493	6,077	3,653	16,223
Balance as of beginning-of-year at Dec. 31, 2015	6,298	6,474	845	13,617
Stock compensation/issued for benefit plans	6
Net income (loss)		208		208
Retirement of common stock/cancellation of shares	(142)	(58)
Common stock dividends declared		(59)
Other comprehensive income (loss), net of tax			1,086	1,086
Balance as of end-of-period at Mar. 31, 2016	$ 6,162	$ 6,565	$ 1,931	$ 14,658