Pension and Employee Benefit Plans - Schedule of Changes in Projected Benefit Obligations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in projected benefit obligation:
Service cost	$ 233	$ 204	$ 126
Interest cost	1,412	1,428	676
Change in plan assets:
Fair value of plan assets at beginning of year	27,302
Fair value of plan assets at end of year	25,296	27,302
Accumulated other comprehensive income (loss):
Amount recognized in accumulated other comprehensive income (loss)	$ (5,170)	$ (4,878)	$ (826)	$ (2,188)
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	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	$ 38,208	$ 32,311	$ 8,535
Projected benefit obligation from acquisition			24,364
Service cost	233	204	126
Interest cost	1,412	1,428	676
Actuarial (gain)/loss	(1,744)	6,015	(509)
Administrative expenses	(214)	(174)	(126)
Benefits paid	(1,755)	(1,576)	(755)
Projected benefit obligation at end of year	36,140	38,208	32,311
Change in plan assets:
Fair value of plan assets at beginning of year	27,302	25,822	5,549
Fair value of plan assets from acquisition			18,654
Actual return on plan assets	(443)	1,404	2,291
Employer contribution	406	1,826	209
Administrative expenses	(214)	(174)	(126)
Benefits paid	(1,755)	(1,576)	(755)
Fair value of plan assets at end of year	25,296	27,302	25,822
Funded status	(10,844)	(10,906)	(6,489)
Defined benefit liabilities included in other liabilities	(10,844)	(10,906)	(6,489)
Deferred tax benefit (expense) associated with accumulated other comprehensive loss (income)	3,154	2,983	608
Accumulated other comprehensive loss (income), net of tax	5,144	4,865	856
Net amount recognized	(2,546)	(3,058)	(5,025)
Other comprehensive income (loss):
Net loss (gain)	708	6,561	(1,926)
Amortization of prior service cost		(4)	(1)
Amortization of net actuarial loss (gain)	(258)	(173)	(370)
Total recognized in other comprehensive income (loss)	450	6,384	(2,297)
Accumulated other comprehensive income (loss):
Net loss (gain)	8,298	7,848	1,460
Prior service cost			4
Amount recognized in accumulated other comprehensive income (loss)	$ 8,298	$ 7,848	$ 1,464
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	4.00%	3.75%	4.50%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 155	$ 116
Accumulated postretirement benefit obligation	155	116	$ 89
Interest cost	5	5	3
Amendments	9	24	44
Actuarial (gain)/loss	18	38	8
Benefits paid	(28)	(28)	(28)
Projected benefit obligation at end of year	159	155	116
Change in plan assets:
Employer contribution	28	28	28
Benefits paid	(28)	(28)	(28)
Funded status	(159)	(155)	(116)
Defined benefit liabilities included in accounts payable and accrued expenses	(26)	(25)	(21)
Defined benefit liabilities included in other liabilities	(133)	(130)	(95)
Deferred tax benefit (expense) associated with accumulated other comprehensive loss (income)	15	8	(18)
Accumulated other comprehensive loss (income), net of tax	27	14	(27)
Net amount recognized	(117)	(133)	(161)
Other comprehensive income (loss):
Net loss (gain)	17	38	8
Prior service cost	9	24	44
Amortization of prior service cost	(9)	(6)
Amortization of net actuarial loss (gain)	3	11	14
Total recognized in other comprehensive income (loss)	20	67	66
Accumulated other comprehensive income (loss):
Net loss (gain)	(20)	(40)	(89)
Prior service cost	62	62	44
Amount recognized in accumulated other comprehensive income (loss)	$ 42	$ 22	$ (45)
Weighted-average assumptions used to determine benefit obligations for the year ended December 31:
Discount rate	3.00%	3.75%	4.50%