Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Tax Cuts and Jobs Act of 2017, Reclassification of Deferred Income Tax Assets Into Income Taxes Receivable Payable	$ 793
Stock-based compensation	2,000,000	$ 7,000,000
Income Taxes Receivable, Sequestration Fee Payable	53
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	3,000,000
Discontinued Operations, Held-for-sale | Run-Off Life and Annuity Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating loss carryforwards	0
U.S.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating loss carryforwards	$ 3,087,000,000