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
Purchased Impaired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	$ 147,210	$ 157,918
Interest income	(49,017)	(37,819)
Reclassifications from nonaccretable balance	36,718	27,111
Balance at end of period	134,911	147,210
Other Acquired [Member]
Summary of changes in Accretable Yield for acquired loans
Balance at beginning of period	96,907	133,162
Interest income	(36,452)	(63,856)
Reclassifications from nonaccretable balance	15,534	22,849
Other	(3,909)	4,752
Balance at end of period	$ 72,080	$ 96,907