Loans and Leases - Summary of Changes in Accretable Yield for Acquired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Purchased Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 147,210	$ 157,918	$ 154,233
Interest income	(49,017)	(37,819)	(47,452)
Reclassifications from nonaccretable balance	36,718	27,111	51,137
Balance at end of period	134,911	147,210	157,918
Other Acquired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	96,907	133,162	201,153
Interest income	(36,452)	(63,856)	(82,605)
Reclassifications from nonaccretable balance	15,534	22,849	16,437
Other	(3,909)	4,752	(1,823)
Balance at end of period	$ 72,080	$ 96,907	$ 133,162