Summary of Significant Accounting Policies - Adjustments Made Due to ASU 2014-09 Impact on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Inventories, net	$ 166	$ 149	$ 154
Prepaid expenses and contract assets	33	41	34
Equity
Net Former Parent investment	0	845	844
Additional paid-in capital	1,929		0
Balances without adoption of ASC 606
Assets
Inventories, net	173		154
Prepaid expenses and contract assets	25		34
Equity
Net Former Parent investment			$ 844
Additional paid-in capital	1,928
Adjustments due to ASU 2014-09 | ASU 2014-09
Assets
Inventories, net	(6)	(5)
Prepaid expenses and contract assets	8	7
Equity
Net Former Parent investment		$ 1
Additional paid-in capital	$ 1