Employee Benefits - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) shares	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Installment shares	Sep. 30, 2015 USD ($) Installment shares	Dec. 31, 2015 USD ($)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Healthcare benefit expense, net of employee contributions	$ 3,700,000	$ 3,000,000	$ 11,400,000	$ 8,900,000
Accrued compensation	17,464,000		17,464,000		$ 14,488,000
Workers' compensation expense	3,400,000	2,600,000	$ 9,200,000	$ 6,600,000
Common stock granted, shares | shares			143,528
Unrecognized compensation expense	3,400,000		$ 3,400,000
Common nonvested shares, compensation cost not yet recognized, period for recognition			2 years 6 months
2014 Omnibus Incentive Plan [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Common stock granted, shares | shares			100,000	100,000
Share based compensation expenses	400,000	$ 600,000	$ 1,200,000	$ 1,200,000
Number of equal installments for vesting common stock | Installment			3	3
Number of shares surrendered to satisfy tax withholding obligations | shares			32,000
Share based compensation, recognized tax benefits	$ 0		$ 300,000
Common stock vested percentage				100.00%
Common stock shares available for issuance | shares	2,700,000		2,700,000
2014 Omnibus Incentive Plan [Member] | Directors [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Common stock granted, shares | shares			9,000	13,000
Share based compensation expenses			$ 300,000	$ 300,000
Medical IBNR Included in Accrued Compensation [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Accrued compensation	$ 1,600,000		$ 1,600,000		$ 1,500,000