Fair Value Measurements - Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
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	123,770	121,666
Fair Value	$ 152,422	$ 135,181