Long-Term Debt, Short-Term Debt, and Financing Arrangements - Notes Payable (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Outstanding borrowings at end of year	$ 87	$ 85
Notes Payable Current
Short-term Debt [Line Items]
Outstanding borrowings at end of year	$ 87	$ 85
Weighted average interest rate on outstanding borrowings at end of year(b)	2.80%	3.20%
Approximate maximum month-end outstanding borrowings during year	$ 193	$ 178
Approximate average month-end outstanding borrowings during year	$ 177	$ 118
Weighted average interest rate on average month-end outstanding borrowings during year(b)	2.40%	3.00%