Recently Issued Accounting Standards (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement, Effect of Adoption on Total Shareholders' Equity				$ 140
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement, Effect of Adoption on Total Shareholders' Equity		$ 38
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement, Effect of Adoption on Total Shareholders' Equity			$ 31
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement, Effect of Adoption on Noncurrent Assets	$ 1,100
New Accounting Pronouncement, Effect of Adoption on Noncurrent Liabilities	$ 1,200