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
	Mar. 31, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
Contractual interest	$ 4,492	$ 4,492
Amortization of discount	1,209	1,162
Total interest expense recognized	$ 5,701	$ 5,654