Debt, net - Additional Information (Detail)		3 Months Ended		6 Months Ended
	Oct. 05, 2017 USD ($)	Jun. 30, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Debt Instrument [Line Items]
Debt Conversion, Converted Instrument, Amount		$ 579.77062
Deferred finance costs, net		820,000	$ 1,058,000	$ 820,000
Amortization of deferred financing fees				238,000	$ 574,000
3.75% convertible senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 120,000,000	118,923,000		118,923,000
Debt Instrument, Unamortized Discount		$ 7,588,000		$ 7,588,000
Effective interest rate of liability component		8.00%		8.00%
Debt Instrument, Convertible, Carrying Amount of Equity Component		$ 16,847,000		$ 16,847,000
Interest rate percentage	3.75%	3.75%	3.75%	3.75%
Early Repayment of Senior Debt			$ 1,077,000
Common Stock [Member]
Debt Instrument [Line Items]
Debt Conversion, Converted Instrument, Shares Issued | shares		8.17192
Debt Conversion, Converted Instrument, Shares Issued	0.0408351
Other [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Debt instrument, collateral amount		$ 10,000,000		$ 10,000,000
Keybank National Association [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity under letter of credit facility		30,000,000		30,000,000
Debt instrument, collateral amount		30,000,000		30,000,000
Letters of credit outstanding		$ 21,474,000		$ 21,474,000