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Derivative Instruments - Interest rate swaps (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2021	Dec. 31, 2019
Derivative [Line Items]
Interest expense related to payments on interest rate swaps	$ 6,924	$ 6,459	$ 14,086	$ 13,605
Reclassification of other comprehensive income to interest expense	2,700	500	3,500	1,000
Interest Rate Swap
Derivative [Line Items]
Derivative instruments, notional amount	700,000		700,000
Ineffectiveness recognized	0	$ 0	0	$ 0
Cash flow hedging \| Interest Rate Swap
Derivative [Line Items]
Derivative Liability, fair Value	58,300		58,300			$ 19,900
Unsecured Credit Facility, Term Loan \| Interest Rate Swap
Derivative [Line Items]
Aggregate principal amount	700,000		700,000
Unsecured Credit Facility, Term Loan A, Matures on December 17, 2024 \| Interest Rate Swap
Derivative [Line Items]
Aggregate principal amount	225,000		225,000
Unsecured Credit Facility, Term Loan B, Matures on April 27 2025 \| Interest Rate Swap
Derivative [Line Items]
Aggregate principal amount	225,000		225,000
Unsecured Credit Facility, Term Loan C, Matures on October 18 2026 \| Interest Rate Swap
Derivative [Line Items]
Aggregate principal amount	$ 250,000		$ 250,000
Forecast
Derivative [Line Items]
Reclassification of other comprehensive income to interest expense					$ 2,000