Borrowings - European Revolving Credit Facility and Term Loan (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 SEK (kr)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Line of Credit Facility [Line Items]
Debt outstanding		$ 2,610,574	$ 2,847,002
European Revolving Credit Facility
Line of Credit Facility [Line Items]
Loan-to-value covenant	45.00%
European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity		340,000
Debt Instrument, covenant, interest bearing deposits, maximum | kr	kr 1,200,000,000
European Revolving Credit Facility | Overdraft Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		40,000
Facility line fee	0.125%
Line of Credit | Europe revolving credit
Line of Credit Facility [Line Items]
Debt outstanding		999,971	$ 1,017,465
Line of Credit | European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line Of Credit Facility, Additional Borrowing Capacity		200,000
Debt Instrument, Additional Term	2 years
Maximum borrowing capacity		1,300,000
Unused commitment fee	1.23%
Unused line fee as a percentage of margin	35.00%
Current borrowing capacity		97,400
Debt instrument, covenant, maximum GIBD	3.25
Minimum | Line of Credit | European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line Of Credit Facility, Accordion Feature, Increase Limit		50,000
Minimum | Interbank Offered Rate (IBOR) | Line of Credit | European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread variable rate	2.70%
Maximum | Line of Credit | European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line Of Credit Facility, Accordion Feature, Increase Limit		$ 500,000
Maximum | Interbank Offered Rate (IBOR) | Line of Credit | European Revolving Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread variable rate	3.80%