Exchangeable Senior Notes - Interest Cost Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Contractual interest	$ 13,476	$ 17,968	$ 18,106
Amortization of discount	3,675	4,742	4,687
Total interest expense recognized	$ 17,151	$ 22,710	$ 22,793

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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