Securities (Other Than Temporary Impairment Recognized) (Detail) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Investments, Unrealized Loss Position
OTTI	[1]	$ (3,000,000)	$ (4,000,000)	$ (5,000,000)	$ (5,000,000)
Available-for-sale securities | Equity securities
Investments, Unrealized Loss Position
OTTI				(1,000,000)
Available-for-sale securities | Debt securities
Investments, Unrealized Loss Position
OTTI		$ (3,000,000)	$ (4,000,000)	$ (4,000,000)	$ (5,000,000)

[1] (a) Included in securities gains, net, in the Condensed Consolidated Statements of Income.