Loans, Leases and Allowance for Credit Losses - Tabular Disclosure of Nonperforming Assets (Detail) - USD ($) $ in Thousands		Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	$ 30,071		$ 40,272
Loans past due 90 days or more on accrual status		4,021		1,067
Troubled debt restructured loans		44,221		53,637
Total nonperforming loans		78,313		94,976
Other assets acquired through foreclosure, net		30,988	$ 45,200	47,815	$ 49,842	$ 52,776	$ 43,942
Total nonperforming assets		109,301		142,791
Troubled Debt Restructured Loans [Member]
Financing Receivable, Recorded Investment, Nonaccrual Status		11,000		7,100
Receivables Acquired with Deteriorated Credit Quality [Member]
Loans past due 90 days or more on accrual status		$ 300		$ 100

[1] Includes non-accrual TDR loans of $11.0 million and $7.1 million at June 30, 2017 and December 31, 2016, respectively.