Summary of Additional Interest Expense Recognized (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Interest Expenses [Line Items]
Total	$ 28,404	$ 27,082	$ 5,482
Convertible Notes due 2018
Schedule Of Interest Expenses [Line Items]
Amortization of issuance costs	1,921	1,910	397
Accretion of debt discount	13,633	12,963	2,620
Convertible Notes due 2020
Schedule Of Interest Expenses [Line Items]
Amortization of issuance costs	1,283	1,279	264
Accretion of debt discount	$ 11,567	$ 10,930	$ 2,201