Fair Value Measurements (Fair Value of Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets:
Available-for-sale securities	$ 56	$ 457
Total | Government, agency, and government-sponsored enterprise obligations
Assets:
Available-for-sale securities	51	444
Total | Corporate bonds
Assets:
Available-for-sale securities	5	7
Total | Common stock and equivalents
Assets:
Available-for-sale securities		6
Total | Foreign exchange derivative contracts
Assets:
Foreign exchange derivative contracts	9	6
Liabilities:
Foreign exchange derivative contracts	32	2
Total | Interest rate swap
Liabilities:
Foreign exchange derivative contracts		1
Level 1 | Government, agency, and government-sponsored enterprise obligations
Assets:
Available-for-sale securities		0
Level 1 | Corporate bonds
Assets:
Available-for-sale securities		0
Level 1 | Common stock and equivalents
Assets:
Available-for-sale securities		6
Level 1 | Foreign exchange derivative contracts
Assets:
Foreign exchange derivative contracts		0
Liabilities:
Foreign exchange derivative contracts		0
Level 1 | Interest rate swap
Liabilities:
Foreign exchange derivative contracts		0
Level 2 | Government, agency, and government-sponsored enterprise obligations
Assets:
Available-for-sale securities	51	444
Level 2 | Corporate bonds
Assets:
Available-for-sale securities	5	7
Level 2 | Common stock and equivalents
Assets:
Available-for-sale securities		0
Level 2 | Foreign exchange derivative contracts
Assets:
Foreign exchange derivative contracts	9	6
Liabilities:
Foreign exchange derivative contracts	$ 32	2
Level 2 | Interest rate swap
Liabilities:
Foreign exchange derivative contracts		$ 1