Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2018

Valuation and Qualifying Accounts [Abstract]

Schedule II - Valuation and Qualifying Accounts

Schedule II

Valuation and Qualifying Accounts

For the Years Ended December 31, 2018, 2017 and 2016

(In millions) Description	Balance at Beginning of Period		Additions Charged to Costs and Expenses		Deductions (a)		Other		Balance at End of Period
Allowance for doubtful accounts:
2018	$	7	$	17	$	16	$	—	$	8
2017	10		20		23		—		7
2016	18		18		26		—		10
Obsolescence allowance—spare parts:
2018	$	354	$	73	$	15	$	—	$	412
2017	295		75		17		1		354
2016	235		61		16		15		295
Valuation allowance for deferred tax assets:
2018	$	63	$	2	$	6	$	—	$	59
2017	68		11		27		11		63
2016	48		47		27		—		68

(a) Deduction from reserve for purpose for which reserve was created.