Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2016

Valuation and Qualifying Accounts [Abstract]

Schedule of Valuation and Qualifying Accounts

The table below provides changes in the allowance for doubtful accounts over each period.

(in millions)	2016			2015			2014
Balance at beginning of year	$	22		$	24		$	22
Additions charged to expense	4			4			9
Deductions/other	(5		)	(6		)	(7		)
Balance at end of year	$	21		$	22		$	24