Exchangeable Senior Notes - Summary of Amount of Interest Cost Recognized Relating to Contractual Interest Rates and Amortization of Discounts on Liability Components of Notes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Debt Disclosure [Abstract]
Contractual interest	$ 4,867	$ 1,484	$ 9,749	$ 2,968
Amortization of discount	1,240	696	2,473	1,393
Total interest expense recognized	$ 6,107	$ 2,180	$ 12,222	$ 4,361