Nature of Operations and Basis of Presentation - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards		$ (1,144)
Accounting Standards Update 2016-02 [Member] | Right-of-use Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	$ 1,000
Accounting Standards Update 2016-02 [Member] | Noncancelable Operating Lease Obligations [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of accounting standards	$ 1,000