Senior Convertible Notes - Summary of Difference between Aggregate Fair Value and Aggregate Unpaid Principal Balance of Senior Convertible Notes Recorded at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Option, Quantitative Disclosures [Line Items]
Total Senior Convertible Notes, Aggregate fair value	$ 0	$ 91,874
Total Senior Convertible Notes, Aggregate unpaid principal balance		71,743
Total Senior Convertible Notes, Fair value over unpaid principal balance		20,131
Senior Convertible Notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Total Senior Convertible Notes, Aggregate fair value		28,135
Total Senior Convertible Notes, Aggregate unpaid principal balance		22,547
Total Senior Convertible Notes, Fair value over unpaid principal balance		5,588
Senior Convertible Notes [Member] | March 2013 Investor Notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Total Senior Convertible Notes, Aggregate fair value		24,482
Total Senior Convertible Notes, Aggregate unpaid principal balance		19,567
Total Senior Convertible Notes, Fair value over unpaid principal balance		4,915
Senior Convertible Notes [Member] | March 2013 Arcapita Notes [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Total Senior Convertible Notes, Aggregate fair value		3,653
Total Senior Convertible Notes, Aggregate unpaid principal balance		2,980
Total Senior Convertible Notes, Fair value over unpaid principal balance		$ 673