Loans and Leases - Summary of Changes in Accretable Yield for Acquired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Purchased Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 157,918	$ 154,233	$ 184,618
Interest income	(37,819)	(47,452)	(52,769)
Reclassifications from nonaccretable balance	27,111	51,137	22,384
Balance at end of period	147,210	157,918	154,233
Other Acquired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	133,162	201,153	296,434
Interest income	(63,856)	(82,605)	(123,044)
Reclassifications from nonaccretable balance	22,849	16,437	22,677
Other	4,752	(1,823)	5,086
Balance at end of period	$ 96,907	$ 133,162	$ 201,153