Total Interest Expense Recognized Related to Convertible Notes (Detail) (Senior Notes, USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Senior Notes
Schedule Of Interest Expenses [Line Items]
Contractual interest expense	$ 1,812	$ 2,074
Amortization of debt discount	1,872	2,141
Amortization of debt issuance costs	33	38
Total interest expense	$ 3,717	$ 4,253