Consolidated Statement of Shareholder's Interest - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Shareholder's Interest [Roll Forward]
Balance at beginning of period			$ 11,713	$ 11,367
Shareholder's Interest Attributable to Noncontrolling Interest			1	0
Total Shareholder's Interest			11,714	11,367
Net income	$ 386	$ 365	1,040	1,011
Net Income (Loss) Attributable to Noncontrolling Interest			0	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			1,040	1,011
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent			(41)	(562)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest			0	1
Other Comprehensive Income (Loss), Net of Tax	(72)	(275)	(41)	(561)
Distributions			(1)	(56)
Balance at end of period	12,712	11,760	12,712	11,760
Shareholder's Interest Attributable to Noncontrolling Interest	0	1	0	1
Total Shareholder's Interest	12,712	11,761	12,712	11,761
Shareholder's Interest [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period			5,227	5,227
Net income			0	0
Other Comprehensive Income (Loss), Net of Tax			0	0
Distributions			0	0
Balance at end of period	5,227	5,227	5,227	5,227
Accumulated Other Comprehensive Income/(Loss) [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period			(607)	160
Net income			0	0
Other Comprehensive Income (Loss), Net of Tax	(72)	(275)	(41)	(562)
Distributions			0	0
Balance at end of period	(648)	(402)	(648)	(402)
Retained Earnings [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period			7,093	5,980
Net income			1,040	1,011
Other Comprehensive Income (Loss), Net of Tax			0	0
Distributions			0	(56)
Balance at end of period	$ 8,133	$ 6,935	8,133	6,935
Parent [Member]
Shareholder's Interest [Roll Forward]
Distributions			0	(56)
Noncontrolling Interest [Member]
Shareholder's Interest [Roll Forward]
Distributions			$ (1)	$ 0