Fair Value Measurements - Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets:
Foreign exchange derivative contracts	$ 4
Common stock	10
Available-for-sale securities:		$ 15
Liabilities:
Foreign exchange derivative contracts	8
Recurring basis | Estimate of Fair Value, Fair Value Disclosure | Corporate bonds
Assets:
Corporate bonds	2
Available-for-sale securities:		2
Recurring basis | Estimate of Fair Value, Fair Value Disclosure | Common stock
Assets:
Common stock	10
Available-for-sale securities:		13
Recurring basis | Estimate of Fair Value, Fair Value Disclosure | Foreign exchange contracts
Assets:
Foreign exchange derivative contracts	4	5
Liabilities:
Foreign exchange derivative contracts	8	5
Recurring basis | Level 1 | Corporate bonds
Assets:
Corporate bonds	0
Available-for-sale securities:		0
Recurring basis | Level 1 | Common stock
Assets:
Common stock	0
Available-for-sale securities:		13
Recurring basis | Level 1 | Foreign exchange contracts
Assets:
Foreign exchange derivative contracts	0	0
Liabilities:
Foreign exchange derivative contracts	0	0
Recurring basis | Level 2 | Corporate bonds
Assets:
Corporate bonds	2
Available-for-sale securities:		2
Recurring basis | Level 2 | Common stock
Assets:
Common stock	10
Available-for-sale securities:		0
Recurring basis | Level 2 | Foreign exchange contracts
Assets:
Foreign exchange derivative contracts	4	5
Liabilities:
Foreign exchange derivative contracts	$ 8	$ 5