Income Taxes - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Net operating loss carryforward - US	$ 811	$ 1,049
Net operating loss carryforward - Non-US	180	178
Market value difference of loan portfolio	102	102
Accruals	122	117
Tax credits	789	388
Other	157	111
Total deferred tax assets before valuation allowance	2,161	1,945
Less: valuation allowance	(326)	(144)
Total deferred tax assets	1,835	1,801
Deferred tax liabilities
Depreciable assets	1,619	1,482
Deferred acquisition costs	130	177
Other	125	123
Total deferred tax liabilities	1,874	1,782
Net deferred tax (liability) asset	$ (39)
Net deferred tax (liability) asset		$ 19