Pension and Employee Benefit Plans - Schedule of Changes in Projected Benefit Obligations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in projected benefit obligation:
Service cost	$ 447	$ 233	$ 204
Interest cost	1,426	1,412	1,428
Change in plan assets:
Fair value of plan assets at beginning of year	25,296
Fair value of plan assets at end of year	24,063	25,296
Accumulated other comprehensive income:
Amount recognized in accumulated other comprehensive income	$ (5,083)	$ (5,170)	$ (4,878)	$ (826)
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	4.00%	3.75%	4.50%
Compensation increase rate	0.00%	0.00%	0.00%
Pension Plan [Member]
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 36,140	$ 38,208	$ 32,311
Service cost	447	233	204
Interest cost	1,426	1,412	1,428
Actuarial (gain)/loss	301	(1,744)	6,015
Administrative expenses	(606)	(214)	(174)
Benefits paid	(2,696)	(1,755)	(1,576)
Projected benefit obligation at end of year	35,012	36,140	38,208
Change in plan assets:
Fair value of plan assets at beginning of year	25,296	27,302	25,822
Actual return (loss) on plan assets	2,040	(443)	1,404
Employer contribution	29	406	1,826
Administrative expenses	(606)	(214)	(174)
Benefits paid	(2,696)	(1,755)	(1,576)
Fair value of plan assets at end of year	24,063	25,296	27,302
Funded status	(10,949)	(10,844)	(10,906)
Defined benefit liabilities included in other liabilities	(10,949)	(10,844)	(10,906)
Deferred tax benefit associated with accumulated other comprehensive loss	3,107	3,154	2,983
Accumulated other comprehensive loss, net of tax	5,074	5,144	4,865
Net amount recognized	(2,768)	(2,546)	(3,058)
Other comprehensive income (loss):
Net loss (gain)	90	708	6,561
Amortization of prior service cost			(4)
Amortization of net actuarial loss (gain)	(212)	(258)	(173)
Total recognized in other comprehensive income (loss)	(122)	450	6,384
Accumulated other comprehensive income:
Net loss (gain)	8,181	8,298	7,848
Amount recognized in accumulated other comprehensive income	$ 8,181	$ 8,298	$ 7,848
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	3.85%	4.00%	3.75%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Change in projected benefit obligation:
Accumulated postretirement benefit obligation at beginning of year	$ 159	$ 155	$ 116
Interest cost	4	5	5
Amendments		9	24
Actuarial (gain)/loss	(8)	18	38
Benefits paid	(24)	(28)	(28)
Accumulated postretirement benefit obligation at end of year	131	159	155
Change in plan assets:
Employer contribution	24	28	28
Benefits paid	(24)	(28)	(28)
Funded status	(131)	(159)	(155)
Defined benefit liabilities included in accounts payable and accrued expenses	(25)	(26)	(25)
Defined benefit liabilities included in other liabilities	(106)	(133)	(130)
Deferred tax benefit associated with accumulated other comprehensive loss	15	15	8
Accumulated other comprehensive loss, net of tax	9	27	14
Net amount recognized	(107)	(117)	(133)
Other comprehensive income (loss):
Net loss (gain)	(9)	17	38
Prior service cost		9	24
Amortization of prior service cost	(10)	(9)	(6)
Amortization of net actuarial loss (gain)	1	3	11
Total recognized in other comprehensive income (loss)	(18)	20	67
Accumulated other comprehensive income:
Net loss (gain)	(28)	(20)	(40)
Prior service cost	52	62	62
Amount recognized in accumulated other comprehensive income	$ 24	$ 42	$ 22
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	2.75%	3.00%	3.75%