Fair Value Measurements - Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
2006 Convertible Senior Subordinated Notes [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input [Line Items]
Carrying Value	$ 750	$ 750
Fair Value	750	750
2010 Convertible Senior Subordinated Notes [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input [Line Items]
Carrying Value	48,067	95,819
Fair Value	$ 64,220	$ 118,157