Income Taxes (Income Taxes - Additional Information) (Detail) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016
Income Taxes
Applicable income tax expense	$ 127	$ 103	[1],[2]	$ 218	$ 212	[3]
Effective tax rate	25.90%	23.90%		24.50%	24.50%
Net tax deficiency reclassified from capital surplus to applicable income tax expense		$ 5			$ 6

[1] A net tax deficiency of $ 5 was reclassified from capital surplus to applicable income tax expense for the three months ended June 30, 2016, related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effe ctive date of January 1, 2016.

[2] Net tax deficiencies of $ 5 and $6 were reclassified from capital surplus to applicable income tax expense and average common shares out standing – diluted were adjusted for t he three and six months ended June 30, 2016, respectively, related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effective date of January 1, 2016.

[3] Net tax deficiencies of $ 6 were reclassified from capital surplus to applicable income tax expense for the six months ended June 30, 2016 related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effective d ate of January 1, 2016