Organization and Summary of Significant Accounting Policies - Revenue Initial Application Period Cumulative Effect Transition (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable - Trade	$ 1,065	$ 1,009	$ 994
Other current assets	102	98	97
Other accrued liabilities	269	236	$ 220
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable - Trade	16	15
Other current assets	2	1
Other accrued liabilities	18	$ 16
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable - Trade	1,049
Other current assets	100
Other accrued liabilities	$ 251