Basis of Presentation and Accounting Policies Level 4 (Details) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings		$ 193
Unrealized Loss on Securities			$ 423	$ 203	$ (631)
Available-for-sale Securities, Equity Securities		154	154	152
Other Comprehensive Income (Loss), Net of Tax			301	129	(628)
Maximum uncollateralized threshold for derivative counter party, single level entity			$ 10
Gross profit estimates term			20 years
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized Loss on Securities	$ 11		$ 428	$ 212	$ (633)
Available-for-sale Securities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Available-for-sale Securities, Equity Securities		$ 154	154
Available-for-sale Securities [Member] | Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Comprehensive Income (Loss), Net of Tax			3
Dividend Paid [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash Dividends Paid to Parent Company			$ 1,400