Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Realized gains	$ 3,429	$ 87	$ 7,466	$ 654
Realized losses	(124)	(185)	(1,396)	(252)
Net realized gains (losses)	3,305	(98)	6,070	402
Other than temporary impairment charges	0	0	0	0
Gains (losses) on investment securities, net	3,305	(98)	6,070	402
Proceeds from sales and calls of available-for-sale securities	1,114,666	82,827	2,186,662	1,216,860
Proceeds from calls of held-to-maturity securities	$ 141,885	$ 0	$ 423,866	$ 0