Income Taxes Income Tax Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Current Federal Tax Expense (Benefit)	$ 1,286	$ 999	$ 1,211
Current State Tax Expense (Benefit)	163	127	168
Total Current Income Tax Expense (Benefit)	1,449	1,126	1,379
Deferred Federal Income Tax Expense (Benefit)	(6,555)	901	1,097
Deferred State Income Tax Expense (Benefit)	134	97	51
Total Deferred Income Tax Expense (Benefit)	(6,421)	998	1,148
Total Income Tax Expense (Benefit)	$ (4,972)	$ 2,124	$ 2,527