Allowance for Credit Losses - Summary of Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		$ 102,353	$ 113,617
Loans charged-off	[1]	(14,972)	(26,898)	[2]
Charged-off loans recovered	[3]	10,951	12,189
Net charge-offs		(4,021)	(14,709)
Provision for loan losses		7,846	3,445
Ending balance		106,178	102,353
Covered loans charge-offs		200	1,500
Covered loans recovered			462
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		43,676	51,551
Loans charged-off	[1]	(7,928)	(12,722)	[2]
Charged-off loans recovered	[3]	7,233	6,874
Net charge-offs		(695)	(5,848)
Provision for loan losses		5,786	(2,027)
Ending balance		48,767	43,676
Commercial and industrial [Member] | Non-Performing Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans charged-off		(4,800)
Commercial real estate loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		42,840	42,343
Loans charged-off	[1]	(2,790)	(9,470)	[2]
Charged-off loans recovered	[3]	1,759	3,110
Net charge-offs		(1,031)	(6,360)
Provision for loan losses		6,197	6,857
Ending balance		48,006	42,840
Commercial real estate loans [Member] | Non-Performing Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Loans charged-off		(4,000)
Residential mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		5,093	7,786
Loans charged-off	[1]	(813)	(1,004)	[2]
Charged-off loans recovered	[3]	421	248
Net charge-offs		(392)	(756)
Provision for loan losses		(76)	(1,937)
Ending balance		4,625	5,093
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		5,179	4,359
Loans charged-off	[1]	(3,441)	(3,702)	[2]
Charged-off loans recovered	[3]	1,538	1,957
Net charge-offs		(1,903)	(1,745)
Provision for loan losses		1,504	2,565
Ending balance		4,780	5,179
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance		5,565	7,578
Loans charged-off	[1]	0	0	[2]
Charged-off loans recovered	[3]	0	0
Net charge-offs		0	0
Provision for loan losses		(5,565)	(2,013)
Ending balance		$ 0	$ 5,565

[1] Includes covered loans charge-offs totaling $200 thousand and $1.5 million during 2015 and 2014, respectively, primarily in the commercial and industrial loan and commercial real estate loan portfolios, respectively

[2] The commercial and industrial loan and commercial real estate loan categories included $4.8 million and $4.0 million of charge-offs, respectively, related to the valuation of non-performing loans transferred to loans held for sale during 2014.

[3] Includes covered loan recoveries totaling $462 thousand during 2014. There were no covered loan recoveries during 2015.