Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details 5) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement, Early Adoption [Line Items]
Net earnings	$ 525	$ 602	$ 517	$ 556	$ 459	$ 516	$ 531	$ 484	$ 2,200	$ 1,990	$ 2,069
Net Cash Provided by (Used in) Operating Activities									2,813	2,162	2,593
Net Cash Provided by (Used in) Financing Activities									(1,786)	$ (3,275)	$ (3,235)
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Net earnings									85
Net Cash Provided by (Used in) Operating Activities									85
Net Cash Provided by (Used in) Financing Activities									$ 85