Income Taxes - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended			24 Months Ended
	Apr. 01, 2017	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2017	Jul. 01, 2016
Income Taxes [Line Items]
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)			$ (4)	$ 61
Write down of deferred tax asset due to tax rate change			(3)	37
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)			(1)	24
Less: Valuation allowance			$ 36	43
Realization assessment period			3 years
Interest and penalties related to uncertain tax positions			$ 1	1	$ 2
Accrued interest for uncertain tax positions			2	3
Unrecognized Tax Benefits that Would Impact Effective Tax Rate			16	31
Tax Adjustments, Settlements, and Unusual Provisions		$ 37	18
FTC from previous acquisitions			13
Tax Cuts and Jobs Act of 2017, Deferred Tax Assets, Tax Credit Carryforwards, Foreign			23
FTC due to Tax Act			0	$ 31
FTC that are more than likely to not be utilized			36
Tax Cuts and Jobs Act of 2017, Deferred tax expense			34
Tax Cuts and Jobs Act of 2017, Accounting Complete, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)			$ 23
Foreign Tax Authority [Member]
Income Taxes [Line Items]
Corporate tax rate			21.00%	35.00%	35.00%
United Kingdom [Member]
Income Taxes [Line Items]
Corporate tax rate	19.00%		19.00%			20.00%
United States [Member]
Income Taxes [Line Items]
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)			$ 4	$ 61
Tax Cuts and Jobs Act of 2017, Income tax expense			57
Alternative Minimum Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Foreign tax credit			20
CIFG Holding Inc. [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards			$ 162				$ 189