Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Mar. 18, 2013
Impaired Long Lived Assets Held And Used [Line Items]
Impairment of long-lived assets			$ 0		$ 0
Fair value of available for sale securities	$ 1,700,000		1,700,000		$ 3,900,000
Change in fair value of available for sale securities	$ (249,000)	$ 299,000	$ (2,227,000)	$ 299,000
Convertible Notes | 1.50% Senior Subordinated Notes Due March 15, 2018
Impaired Long Lived Assets Held And Used [Line Items]
Debt instrument, interest rate, stated percentage	1.50%	1.50%	1.50%	1.50%	1.50%	1.50%