Schedule of Equity (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Payments of Stock Issuance Costs					$ 12
Stock Issued During Period, Shares, New Issues		10,400,000
Proceeds from Issuance of Common Stock			$ 271	$ 0	$ 271
Common Stock, Shares, Outstanding beginning of period	88,792,751			88,792,751
Stockholders' Equity	$ 2,258			$ 2,258
Common Stock, Shares, Outstanding end of period				88,920,756
Stockholders' Equity				$ 2,303
Common Stock [Member]
Common Stock, Shares, Outstanding beginning of period	88,792,751	88,765,629	78,228,339	88,792,751	78,228,339
Issuances of shares pursuant to equity-based plans	128,005		137,290
Common Stock, Shares, Outstanding end of period	88,920,756		88,765,629
Common Stock Including Additional Paid in Capital [Member]
Issuance of shares pursuant to equity-based plans	$ 1		$ 1
Adjustments Related to Tax Withholding for Share-based Compensation	1		1
Stockholders' Equity	1,196	$ 1,191	918	$ 1,196	$ 918
Dividends declared	0		0
Stockholders' Equity	1,198		1,191
AOCI Attributable to Parent [Member]
Stockholders' Equity	(8)	(7)	(7)	(8)	(7)
Stock-based compensation	0		0
Dividends declared	0		0
Stockholders' Equity	(8)		(7)
Retained Earnings [Member]
Stockholders' Equity	1,070	1,037	1,000	1,070	1,000
Stock-based compensation	0		0
Dividends declared	(55)		(48)
Net Income	98		85
Stockholders' Equity	1,113		1,037
Stockholders' Equity, Total [Member]
Issuance of shares pursuant to equity-based plans	1		1
Adjustments Related to Tax Withholding for Share-based Compensation	1		1
Stockholders' Equity	2,258	$ 2,221	1,911	$ 2,258	$ 1,911
Dividends declared	(55)		(48)
Net Income	98		85
Stockholders' Equity	$ 2,303		$ 2,221