Organization and Summary of Significant Accounting Policies (Summary of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization and Summary of Significant Accounting Policies [Abstract]
Cash	$ 32	$ 261
Marketable securities	169	605
Other cash equivalents		50
Total	$ 201	$ 916	$ 1,423	$ 15