Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2014
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible notes, fair value	$ 214,000,000	$ 198,000,000
Convertible notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of debt issued	$ 200,000,000	$ 200,000,000	$ 200,000,000.0