Fair Value Accounting - Gains and Losses from Fair Value Changes Included in Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2017		Mar. 31, 2016	Dec. 31, 2016
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 52,396	[1]		$ 50,410
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(1,987)		$ 1,207
Interest Income on Securities	7		11
Interest Expense on Junior Subordinated Debt	(749)		(680)
Total Changes Included in Current-Period Earnings	(743)		(674)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	(1,229)		759
Securities measured at fair value [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(1)		(5)
Interest Income on Securities	7		11
Interest Expense on Junior Subordinated Debt	0		0
Total Changes Included in Current-Period Earnings	6		6
Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(1,986)		1,212
Interest Income on Securities	0		0
Interest Expense on Junior Subordinated Debt	(749)		(680)
Total Changes Included in Current-Period Earnings	(749)		(680)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (1,229)		$ 759
Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Junior subordinated debt, Input Value	5.54%			5.66%
Level 3 [Member] | Junior Subordinated Debt [Member]
Fair Value, Option, Qualitative Disclosures Related to Election [Line Items]
Subordinated Debt Obligations, Fair Value Disclosure	$ 52,396			$ 50,410
Junior subordinated debt, Valuation Technique	Discounted cash flow			Discounted cash flow
Junior subordinated debt, Significant Unobservable Inputs	Implied credit rating of the Company			Implied credit rating of the Company

[1] Includes only the portion of junior subordinated debt that is recorded at fair value at each reporting period pursuant to the election of FVO treatment.