Available-For-Sale Securities (Narrative) (Detail) (USD $) In Billions, unless otherwise specified	Mar. 31, 2014 securities	Dec. 31, 2013	Mar. 31, 2013
Available-for-sale Securities [Abstract]
Pledged Securities, carrying value	$ 1.2	$ 1.2	$ 1.1
Number of securities by a single non-goverment sponsored issuer exceeding 10% of shareholders' equity	0