Guarantor and Non-Guarantor Consolidating Financial Statements Cash and cash equivalents, program cash and restricted cash (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 615	$ 611
Program cash	115	283
Restricted Cash	5	7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	735	901	$ 720	$ 717
Non-Guarantor Subsidiaries
Cash and cash equivalents	601	593
Program cash	115	283
Restricted Cash	5	7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 721	$ 883	$ 705	$ 643