Fair Value Of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Of Financial Instruments [Abstract]

Fair Value Of Long-Term Debt

	March 31, 2019				December 31, 2018
($ in millions)		Carrying Amount		Fair Value		Carrying Amount		Fair Value
Total debt	$	17,155	$	13,185	$	17,400	$	12,756