Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Realized gains	$ 1,487	$ 14	$ 4,037	$ 567
Realized losses	(47)	(38)	(1,272)	(67)
Net realized gains (losses)	1,440	(24)	2,765	500
Other than temporary impairment charges	0	0	0	0
Gains (losses) on available-for-sale securities, net	1,440	(24)	2,765	500
Proceeds from sales and calls of available-for-sale securities	1,068,795	498,501	1,071,996	1,134,033
Proceeds from calls of held-to-maturity securities	$ 183,738	$ 0	$ 281,981	$ 0