Employee Benefit Plans - Additional Information (Detail)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2018 USD ($) Loan Age shares	Dec. 31, 2017 USD ($)
Defined Contribution Plan Disclosure [Line Items]
Gain on curtailment of post-retirement benefit plan		$ 352,000
Deferred compensation liability		$ 972,000	$ 901,000
Number of employee stock ownership plans	1		2
Noncontributory employee stock ownership plan, service period eligibility		12 months
Noncontributory employee stock ownership plan, age eligibility | Age		21
Allocations, as a percentage of eligible participant compensation		25.00%
Participant accounts vested after two years		30.00%
Participant accounts vested after three years		40.00%
Participant accounts vested each year, from fourth year till 100% vested		20.00%
Participant accounts, total vested		100.00%
Allocated shares | shares		532,240
Contribution expense		$ 0	$ 223,000
Number of outstanding loans | Loan		6
ESOP loan		$ 1,800,000
Unallocated shares to employee | shares		225,930
401 (k) Retirement Plan
Defined Contribution Plan Disclosure [Line Items]
Employees vested percentage in subsidiary’s match after two years of service		100.00%
Matching contributions amount to defined contribution plan		$ 401,000	491,000
401 (k) Retirement Plan, First 3% of Deferral
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan		100.00%
Percentage of employee's contributions		3.00%
401 (k) Retirement Plan, Next 3% of Deferral
Defined Contribution Plan Disclosure [Line Items]
Matching contribution to defined contribution plan		50.00%
Percentage of employee's contributions		3.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Deferred compensation plan, distribution period		20 years
Maximum | 401 (k) Retirement Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, contributions per employee percent		15.00%
Minimum | 401 (k) Retirement Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, contributions per employee percent		1.00%
Executive Officer
Defined Contribution Plan Disclosure [Line Items]
Deferred compensation payments		$ 179,000	107,000
Director
Defined Contribution Plan Disclosure [Line Items]
Deferred compensation payments		$ 61,000	53,000
Nonqualified Plan | Executive Officer | Maximum
Defined Contribution Plan Disclosure [Line Items]
Percentage of nonqualified deferred compensation plan deferred		100.00%
Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Accumulated benefit obligation		$ 1,600,000	3,300,000
Unfunded liability		483,000	808,000
Employer contributions		0
PRB Plan
Defined Contribution Plan Disclosure [Line Items]
Unfunded liability		71,000	457,000
Employer contributions		$ 6,000	6,000
Conditional age-1 for availing plan		55 years
Conditional age-2 for availing plan		65 years
Conditional years of service -1 for availing plan		10 years
Conditional years of service-2 for availing plan		5 years
Gain on curtailment of post-retirement benefit plan		$ 352,000
Expected employer contribution		0
PRB Plan | Unfunded
Defined Contribution Plan Disclosure [Line Items]
Accumulated benefit obligation		$ 71,000	$ 457,000