Debt - Summary of Senior Unsecured Credit Facility (Details) $ in Thousands, € in Millions, £ in Millions, ¥ in Billions	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 JPY (¥)	Jun. 30, 2020 EUR (€)	Jun. 30, 2020 GBP (£)	Mar. 27, 2020 USD ($)	Feb. 20, 2020 USD ($)	Dec. 31, 2019 USD ($)
Senior Unsecured Credit Facility
Debt outstanding	$ 314,518						$ 201,267
Unamortized discount	25,219
Unsecured Term Loans:
Senior Unsecured Credit Facility
Debt outstanding	292,152						0
Unsecured Term Loans: | GBP
Senior Unsecured Credit Facility
Debt outstanding	184,091			£ 150.0		$ 193,100	0
Unamortized discount	$ 1,300
Unsecured Term Loans: | GBP | GBP LIBOR
Senior Unsecured Credit Facility
Variable interest rate (percentage)	0.95%
Unsecured Term Loans: | EUR
Senior Unsecured Credit Facility
Debt outstanding	$ 108,061		€ 96.5		$ 105,900		0
Unsecured Term Loans: | EUR | EURIBOR
Senior Unsecured Credit Facility
Variable interest rate (percentage)	0.95%
Unsecured Revolving Credit Facility:
Senior Unsecured Credit Facility
Debt outstanding	$ 22,366						201,267
Unsecured Revolving Credit Facility: | GBP
Senior Unsecured Credit Facility
Debt outstanding	0						47,534
Unsecured Revolving Credit Facility: | EUR
Senior Unsecured Credit Facility
Debt outstanding	0						131,438
Unsecured Revolving Credit Facility: | JPY
Senior Unsecured Credit Facility
Debt outstanding	$ 22,366	¥ 2.4					$ 22,295
Unsecured Revolving Credit Facility: | JPY | JPY LIBOR
Senior Unsecured Credit Facility
Variable interest rate (percentage)	0.85%