Consolidated Statements of Changes in Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Accumulated Defined Benefit Plans Adjustment	Accumulated Net Unrealized Investment Gain (Loss)
Beginning balance at Dec. 31, 2011	$ 4,136	$ 1,386	$ 1,810	$ 960	$ (20)
Beginning Balance (in shares) at Dec. 31, 2011		138,632,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	486			486
Dividends declared on common stock	(317)			(317)
Other Comprehensive Income (Loss), Net of Tax	(2)					(2)
Ending balance at Dec. 31, 2012	4,303	1,386	1,810	1,129	(22)
Ending Balance (in shares) at Dec. 31, 2012		138,632,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	487			487
Dividends declared on common stock	(342)			(342)
Other Comprehensive Income (Loss), Net of Tax	6					5	1
Capital contribution by parent company	400		400
Ending balance at Dec. 31, 2013	4,854	1,386	2,210	1,274	(16)
Ending Balance (in shares) at Dec. 31, 2013	138,632,324	138,632,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	532			532
Dividends declared on common stock	(370)			(370)
Other Comprehensive Income (Loss), Net of Tax	(10)					(10)
Capital contribution by parent company	190		190
Ending balance at Dec. 31, 2014	$ 5,196	$ 1,386	$ 2,400	$ 1,436	$ (26)
Ending Balance (in shares) at Dec. 31, 2014	138,632,324	138,632,000