Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Other Intangible Assets

Intangible assets and associated amortization expense were as follows at December 31:

millions	2017			2016
Gross carrying amount	$	1,013		$	1,013
Accumulated amortization	(140		)	(109		)
Net carrying amount	$	873		$	904
Amortization expense	$	31		$	32