Long-Term Debt, Short-Term Debt, and Financing Arrangements - Notes Payable (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Outstanding borrowings at end of year	$ 85	$ 58
Notes Payable Current
Short-term Debt [Line Items]
Outstanding borrowings at end of year	$ 85	$ 58
Weighted average interest rate on outstanding borrowings at end of year(b)	3.20%	2.60%
Approximate maximum month-end outstanding borrowings during year	$ 178	$ 124
Approximate average month-end outstanding borrowings during year	$ 118	$ 107
Weighted average interest rate on average month-end outstanding borrowings during year(b)	3.00%	4.00%