Allowance for Loan Losses - Summary of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 52,213	$ 48,814	$ 48,147	$ 47,911
Charge-offs	(1,500)	(5,641)	(8,623)	(8,847)
Recoveries	564	3,528	1,890	4,370
Net (Charge-offs)/ Recoveries	(936)	(2,113)	(6,733)	(4,477)
Provision for loan losses	2,516	3,206	12,379	6,473
Balance at End of Period	53,793	49,907	53,793	49,907
Commercial and Industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	14,771	13,308	10,853	13,668
Charge-offs	(414)	(1,121)	(3,244)	(2,819)
Recoveries	169	272	589	475
Net (Charge-offs)/ Recoveries	(245)	(849)	(2,655)	(2,344)
Provision for loan losses	(2,232)	12	4,096	1,147
Balance at End of Period	12,294	12,471	12,294	12,471
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	15,978	19,018	15,043	20,164
Charge-offs	(93)	(2,361)	(1,808)	(2,738)
Recoveries	264	2,896	662	3,072
Net (Charge-offs)/ Recoveries	171	535	(1,146)	334
Provision for loan losses	4,244	(2,575)	6,496	(3,520)
Balance at End of Period	20,393	16,978	20,393	16,978
Commercial Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	11,701	7,671	12,625	6,093
Charge-offs	(163)	(1,247)	(1,108)	(1,247)
Recoveries	17	129	20	132
Net (Charge-offs)/ Recoveries	(146)	(1,118)	(1,088)	(1,115)
Provision for loan losses	1,356	4,983	1,374	6,558
Balance at End of Period	12,911	11,536	12,911	11,536
Consumer Real Estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	8,418	7,027	8,400	6,333
Charge-offs	(369)	(445)	(891)	(997)
Recoveries	44	132	342	379
Net (Charge-offs)/ Recoveries	(325)	(313)	(549)	(618)
Provision for loan losses	(1,760)	302	(1,518)	1,301
Balance at End of Period	6,333	7,016	6,333	7,016
Other Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,345	1,790	1,226	1,653
Charge-offs	(461)	(467)	(1,572)	(1,046)
Recoveries	70	99	277	312
Net (Charge-offs)/ Recoveries	(391)	(368)	(1,295)	(734)
Provision for loan losses	908	484	1,931	987
Balance at End of Period	$ 1,862	$ 1,906	$ 1,862	$ 1,906