Past Due Loans, Allowance For Credit Losses, Impaired Loans, and TDRs (Detail) - TDRs That Were Restructured $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) loan	Dec. 31, 2014 USD ($) loan	Dec. 31, 2013 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	3	10	39
Pre-Modification Recorded Investment	$ 445	$ 24,619	$ 20,343
Funds Disbursed	0	0	30
Interest and Escrow Capitalized	0	0	63
Charge-offs	0	0	0
Post-Modification Recorded Investment	$ 445	$ 24,619	$ 20,436
Commercial And Industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		7	7
Pre-Modification Recorded Investment		$ 23,852	$ 14,439
Funds Disbursed		0	0
Interest and Escrow Capitalized		0	2
Charge-offs		0	0
Post-Modification Recorded Investment		$ 23,852	$ 14,441
Office, Retail, and Industrial
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		1	6
Pre-Modification Recorded Investment		$ 417	$ 2,275
Funds Disbursed		0	30
Interest and Escrow Capitalized		0	0
Charge-offs		0	0
Post-Modification Recorded Investment		$ 417	$ 2,305
Multi-family
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		1	5
Pre-Modification Recorded Investment		$ 275	$ 1,274
Funds Disbursed		0	0
Interest and Escrow Capitalized		0	57
Charge-offs		0	0
Post-Modification Recorded Investment		$ 275	$ 1,331
Construction
Financing Receivable, Modifications [Line Items]
Number of Loans | loan			2
Pre-Modification Recorded Investment			$ 508
Funds Disbursed			0
Interest and Escrow Capitalized			0
Charge-offs			0
Post-Modification Recorded Investment			$ 508
Other Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans | loan			5
Pre-Modification Recorded Investment			$ 526
Funds Disbursed			0
Interest and Escrow Capitalized			0
Charge-offs			0
Post-Modification Recorded Investment			$ 526
Home equity
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	1	13
Pre-Modification Recorded Investment	$ 120	$ 75	$ 1,189
Funds Disbursed	0	0	0
Interest and Escrow Capitalized	0	0	0
Charge-offs	0	0	0
Post-Modification Recorded Investment	$ 120	$ 75	$ 1,189
1-4 family mortgages
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2		1
Pre-Modification Recorded Investment	$ 325		$ 132
Funds Disbursed	0		0
Interest and Escrow Capitalized	0		4
Charge-offs	0		0
Post-Modification Recorded Investment	$ 325		$ 136