Accounts Receivable and Major Customers - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($) Customer	Jun. 30, 2015 USD ($) Customer	Dec. 31, 2015 USD ($)
Sales Revenue | Customer Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of major customers | Customer	3	3
Revenues, major customers	$ 62.2	$ 96.7
Concentration risk, percentage	93.00%	62.00%
Sales Revenue | Customer Concentration Risk | Major Customer 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 32.1	$ 41.2
Concentration risk, percentage	48.00%	26.00%
Sales Revenue | Customer Concentration Risk | Major Customer 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 16.2	$ 36.1
Concentration risk, percentage	24.00%	23.00%
Sales Revenue | Customer Concentration Risk | Major Customer 3
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenues, major customers	$ 13.9	$ 19.4
Concentration risk, percentage	21.00%	13.00%
Accounts Receivable | Credit Concentration Risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	91.00%	90.00%
Accounts receivable, major customers	$ 20.5		$ 21.1