Consolidated Statement of Shareholder's Interest - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Shareholder's Interest [Roll Forward]
Balance at beginning of period			$ 12,803	$ 11,713
Shareholder's Interest Attributable to Noncontrolling Interest			0	1
Total Shareholder's Interest			12,803	11,714
Net income	$ 446	$ 296	779	654
Net Income (Loss) Attributable to Noncontrolling Interest			0	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			779	654
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent			281	31
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest			0	0
Other Comprehensive Income (Loss), Net of Tax	191	(141)	281	31
Distributions			(28)	(1)
Balance at end of period	13,844	12,398	13,844	12,398
Shareholder's Interest Attributable to Noncontrolling Interest	0	0	0	0
Total Shareholder's Interest	13,844	12,398	13,844	12,398
Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	9		9
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
Shareholder's Interest [Member] | Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	0		0
Accumulated Other Comprehensive Income/(Loss) [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period			(890)	(607)
Net income			0	0
Other Comprehensive Income (Loss), Net of Tax	191	(141)	281	31
Distributions			0	0
Balance at end of period	(609)	(576)	(609)	(576)
Accumulated Other Comprehensive Income/(Loss) [Member] | Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	0		0
Retained Earnings [Member]
Shareholder's Interest [Roll Forward]
Balance at beginning of period			8,466	7,093
Net income			779	654
Other Comprehensive Income (Loss), Net of Tax			0	0
Distributions			(28)	0
Balance at end of period	9,226	$ 7,747	9,226	7,747
Retained Earnings [Member] | Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	9		9
Parent [Member]
Shareholder's Interest [Roll Forward]
Distributions			(28)	0
Parent [Member] | Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	9		9
Noncontrolling Interest [Member]
Shareholder's Interest [Roll Forward]
Distributions			0	$ (1)
Noncontrolling Interest [Member] | Accounting Standards Update 2014-09 [Member]
Shareholder's Interest [Roll Forward]
Adoption of accounting standards	$ 0		$ 0