Investments and Cash Investments and Cash - Cash and Restricted Cash (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Cash	$ 147	$ 118	$ 112	$ 166
Restricted cash	1	9	0	0
Cash and Restricted Cash	$ 148	$ 127	$ 112	$ 166