Investment Securities (Narrative) (Detail)	3 Months Ended
	Mar. 31, 2019 USD ($) security	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Equity securities with readily determinable fair value	$ 27,000,000
Upward adjustments of equity securities without readily determinable fair values	0	$ 131,000
Downward adjustments of equity securities without readily determinable fair values	0	0
Impairment of equity securities without readily determinable fair values	0	537,000
Pledged securities	$ 1,700,000,000	$ 1,500,000,000	$ 1,700,000,000
Number of securities by a single non-government sponsored issuer exceeding 10% of shareholders' equity | security	0