Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

A reconciliation of the beginning and ending amount of allowance for doubtful accounts is as follows for the years ended December 31, 2016, 2015 and 2014 (in millions):

	Year Ended December 31,
	2016		2015			2014
Beginning balance of allowance for doubtful accounts	$	2	$	1		$	1
Bad debt expense	5		2			1
Charge-offs	—		(1		)	(1		)
Ending balance of allowance for doubtful accounts	$	7	$	2		$	1