Description of Business and Accounting Policies Recent Accounting Pronouncements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Adoption of ASU 2016-09
Recent Accounting Pronouncements
Unredeemed Gift Cards Expected Redemption Period	9 months
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 700
Expected effect on Income Tax Expense upon adoption	$ 750
Recent Accounting Pronouncements | Accounting Standards Update 2015-17 [Member]
Recent Accounting Pronouncements
Deferred Tax Assets, Gross, Current		$ 769
Deferred Tax Liabilities, Gross, Current		$ 13