Income Taxes - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended			24 Months Ended
	Apr. 01, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2017	Jul. 01, 2016
Income Taxes [Line Items]
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)			$ 61
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Liability, Provisional Income Tax (Expense) Benefit			(37)
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)			$ 24
Document Fiscal Year Focus			2017
Foreign tax credit			$ 31
Less: Valuation allowance			$ 43	$ 19
Realization assessment period			3 years
Interest and penalties related to uncertain tax positions			$ 1	2	$ 1
Accrued interest for uncertain tax positions			3	$ 7
Tax Adjustments, Settlements, and Unusual Provisions		$ 37
FTC from previous acquisitions			12
FTC due to Tax Act			31
FTC that are more than likely to not be utilized			$ 43
Foreign Tax Authority [Member]
Income Taxes [Line Items]
Corporate tax rate			35.00%
United Kingdom [Member]
Income Taxes [Line Items]
Corporate tax rate	19.00%		19.25%			20.00%
Value added tax rate			20.00%
United States [Member]
Income Taxes [Line Items]
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)			$ 61
Alternative Minimum Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Foreign tax credit			59
CIFG Holding Inc. [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards			$ 182				$ 189