Income Taxes Components of Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of income tax provision [Line Items]
Current Federal Tax Expense (Benefit)	$ 667	$ 707	$ 365
Current State and Local Tax Expense (Benefit)	27	36	29
Current Income Tax Expense (Benefit)	694	743	394
Deferred Federal Income Tax Expense (Benefit)	59	27	99
Deferred State and Local Income Tax Expense (Benefit)	52	(6)	0
Deferred Income Tax Expense (Benefit)	111	21	99
Income Tax Expense (Benefit)	$ 805	$ 764	$ 493