Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2018

Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]

Other comprehensive income (loss) on a pre-tax and after-tax basis

Components of other comprehensive income (loss) on a pre-tax and after-tax basis
	For the years ended December 31,
($ in millions)	2018									2017									2016
	Pre-tax			Tax			After-tax			Pre-tax			Tax			After-tax			Pre-tax			Tax			After-tax
Unrealized net holding gains and losses arising during the period, net of related offsets	$	(1,142	)	$	241		$	(901	)	$	866		$	(304	)	$	562		$	486		$	(170	)	$	316
Less: reclassification adjustment of realized capital gains and losses	(186		)	39			(147		)	374			(131		)	243			(180		)	63			(117		)
Unrealized net capital gains and losses	(956		)	202			(754		)	492			(173		)	319			666			(233		)	433
Unrealized foreign currency translation adjustments	(61		)	13			(48		)	69			(24		)	45			14			(5		)	9
Unamortized pension and other postretirement prior service credit arising during the period	—			2			2			1			—			1			22			(5		)	17
Less: reclassification adjustment of prior service credit amortized into operating costs and expenses	77			(16		)	61			81			(28		)	53			77			(27		)	50
Unamortized pension and other postretirement prior service credit	(77		)	18			(59		)	(80		)	28			(52		)	(55		)	22			(33		)
Other comprehensive (loss) income	$	(1,094	)	$	233		$	(861	)	$	481		$	(169	)	$	312		$	625		$	(216	)	$	409