Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Additional Information [Line Items]
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit)	$ (1,600)
Pre-tax earnings from foreign operations	410	$ 287	$ 288
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	(134)	24	19
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	0	33	(7)
Accrued interest and penalties expense (benefit) related to income taxes included in income tax expense	(5)	5	$ 3
Provisional liability accrued for repatriation of undistributed foreign earnings	125
Undistributed earnings of foreign subsidiaries	1,500
Amount of unrecognized deferred tax liability, bad debt reserve for tax purposes of qualified lender	69
Bad debt reserve for tax purposes of qualified lender	287
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense (Benefit)	(125)
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Affordable Housing Tax Credits, Provisional Income Tax Expense (Benefit)	(76)
Internal Revenue Service (IRS)
Additional Information [Line Items]
Operating Loss Carryforwards	15	19
State and Local Jurisdiction
Additional Information [Line Items]
Operating Loss Carryforwards	$ 241	$ 182