Borrowings - Encore Convertible Notes and Exchangeable Notes (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Debt issued \| $	$ 583,500	$ 672,855
Convertible Notes \| 2020 Convertible Notes
Debt Instrument [Line Items]
Debt issued \| $	$ 0	89,355
Stated interest rate	3.00%
Convertible Notes \| 2021 Convertible Notes
Debt Instrument [Line Items]
Debt issued \| $	$ 161,000	161,000
Stated interest rate	2.875%
Initial conversion price (USD per share)	$ 59.39
Closing stock price at date of issuance (in dollars per share)	$ 47.51
Debt Instrument, Convertible, Conversion Ratio	0.0168386
Convertible Notes \| 2022 Convertible Notes
Debt Instrument [Line Items]
Debt issued \| $	$ 150,000	150,000
Stated interest rate	3.25%
Initial conversion price (USD per share)	$ 45.57
Closing stock price at date of issuance (in dollars per share)	$ 35.05
Debt Instrument, Convertible, Conversion Ratio	0.0219467
Convertible Notes \| 2025 Convertible Notes
Debt Instrument [Line Items]
Debt issued \| $	$ 100,000	100,000
Stated interest rate	3.25%
Initial conversion price (USD per share)	$ 40.00
Closing stock price at date of issuance (in dollars per share)	$ 32.00
Debt Instrument, Convertible, Conversion Ratio	0.025
Exchangeable Notes Payable \| 2023 Exchangeable Notes
Debt Instrument [Line Items]
Debt issued \| $	$ 172,500	$ 172,500
Stated interest rate	4.50%
Initial conversion price (USD per share)	$ 44.62
Closing stock price at date of issuance (in dollars per share)	$ 36.45
Debt Instrument, Convertible, Conversion Ratio	0.022409

The price per share of the conversion feature embedded in the debt instrument.

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