Financial Instruments - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents	[1]	$ 246,947	$ 202,823
Restricted cash		169,763	174,565
Cash, cash equivalents and restricted cash		416,710	377,388	$ 280,485	$ 180,612
Cash
Debt Securities, Available-for-sale [Line Items]
Cash, cash equivalents and restricted cash		180,808	100,773
Money market funds
Debt Securities, Available-for-sale [Line Items]
Cash, cash equivalents and restricted cash		$ 235,902	$ 276,615

[1] We have variable interest entities, which represent a portion of the consolidated balances recorded within these financial statement line items in the consolidated balance sheets (see Note 13 - Portfolio Financings).