Borrowings - Interest Expense (Details) - Convertible notes and exchangeable notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense—stated coupon rate	$ 21,857	$ 23,845	$ 17,518
Interest expense—amortization of debt discount	10,945	12,780	10,888
Total interest expense	$ 32,802	$ 36,625	$ 28,406