Shareholder's Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	$ 3,529
Comprehensive (loss) income, net of tax, Attributable to Parent	(37)		$ 9
Cash dividends paid - preferred stock	2		2
Net transfers from parent	0		(161)
Stockholders' Equity Attributable to Parent Period End	3,510
Preferred Stock, Dividends Per Share, Declared		$ 20.00
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	2		2
Comprehensive (loss) income, net of tax, Attributable to Parent	0		0
Cash dividends paid - preferred stock	0		0
Stock option and incentive plans, net	0
Net transfers from parent			0
Stockholders' Equity Attributable to Parent Period End	2		2
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	3,850		3,812
Comprehensive (loss) income, net of tax, Attributable to Parent	0		0
Cash dividends paid - preferred stock	0		0
Stock option and incentive plans, net	3
Net transfers from parent			4
Stockholders' Equity Attributable to Parent Period End	3,853		3,816
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	171		0
Comprehensive (loss) income, net of tax, Attributable to Parent	(50)		(6)
Cash dividends paid - preferred stock	(2)		(2)
Stock option and incentive plans, net	0
Net transfers from parent			0
Stockholders' Equity Attributable to Parent Period End	136		(8)
AOCL Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	(494)		(526)
Comprehensive (loss) income, net of tax, Attributable to Parent	13		15
Cash dividends paid - preferred stock	0		0
Stock option and incentive plans, net	0
Net transfers from parent			0
Stockholders' Equity Attributable to Parent Period End	(481)		(511)
Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent Period Begin	3,529		3,288
Comprehensive (loss) income, net of tax, Attributable to Parent	(37)		9
Cash dividends paid - preferred stock	(2)		(2)
Stock option and incentive plans, net	3
Net transfers from parent			4
Stockholders' Equity Attributable to Parent Period End	$ 3,510		$ 3,299
ASU 2014-09 | Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings				$ 0
ASU 2014-09 | Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings				0
ASU 2014-09 | Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings				17
ASU 2014-09 | AOCL Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings				0
ASU 2014-09 | Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings				$ 17