Notes and Bonds Payable - Narrative (Details)								3 Months Ended		12 Months Ended
	Feb. 18, 2022 USD ($) ft²	Jun. 01, 2021 USD ($)	May 29, 2020 USD ($)	Mar. 18, 2020 USD ($) swapAgreement	May 31, 2019 USD ($) extensionOption Lender	Jul. 05, 2016 USD ($)	Apr. 24, 2015 USD ($) swapAgreement	Jun. 30, 2021 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 02, 2020 USD ($)	Dec. 11, 2017 USD ($)	Feb. 28, 2014 USD ($) Lender	Oct. 14, 2011 USD ($)
Debt Instrument [Line Items]
Unsecured term loan outstanding										$ 1,813,664,000
Issuance costs										$ 9,245,000
Mortgage Notes | Subsequent Event
Debt Instrument [Line Items]
Amount of debt repaid	$ 11,000,000
Effective Interest rate	4.70%
Debt redeemed, make whole amount	$ 1,600,000
Write off of deferred debt issuance cost	$ 100,000
Extinguishment of Debt, Encumbered Square Footage | ft²	56,762
Debt Instrument, Redemption Price	$ 12,600,000
Unamortized premium	$ 800,000
Interest Rate Swap
Debt Instrument [Line Items]
Number of forward starting swaps | swapAgreement				2
Settlement of swap agreements				$ 4,300,000
Line of Credit | Unsecured Credit Facility
Debt Instrument [Line Items]
Unsecured credit facility																$ 700,000,000
Number of extension options | extensionOption					2
Debt Instrument, Period of Extension Option					6 months
Extension fees as percentage of aggregate commitments					0.0625%
Facility fee on the aggregate amount of commitments										0.20%
Line of Credit | Unsecured Credit Facility | Minimum
Debt Instrument [Line Items]
Facility fee on the aggregate amount of commitments										0.125%
Line of Credit | Unsecured Credit Facility | Maximum
Debt Instrument [Line Items]
Facility fee on the aggregate amount of commitments										0.30%
Line of Credit | Unsecured Credit Facility | LIBOR
Debt Instrument [Line Items]
Percentage of interest in addition to LIBOR										0.90%
Contractual interest rates, basis spread on variable rate										0.90%
Line of Credit | Unsecured Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Percentage of interest in addition to LIBOR										0.775%
Line of Credit | Unsecured Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Percentage of interest in addition to LIBOR										1.45%
Medium-term Notes | Term Loan due 2024
Debt Instrument [Line Items]
Senior notes face value					$ 200,000,000					$ 200,000,000	$ 200,000,000				$ 200,000,000
Number of lenders, term loan | Lender					9										9
Amount of debt repaid						$ 50,000,000
Weighted average interest rate (LOC)										2.37%
Contractual interest rates, basis spread on variable rate										1.00%
Amortization of debt issuance costs									$ 300,000	$ 200,000	200,000	$ 200,000
Unsecured term loan outstanding										200,000,000
Deferred finance costs, gross					$ 700,000
Issuance costs					400,000					$ 540,000	764,000
Medium-term Notes | Term Loan due 2024 | Interest Rate Swap
Debt Instrument [Line Items]
Effective Interest rate										1.95%
Derivative notional amount										$ 75,000,000
Medium-term Notes | Term Loan due 2024 | Minimum
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										0.85%
Medium-term Notes | Term Loan due 2024 | Maximum
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										1.65%
Medium-term Notes | Term Loan due 2024 | LIBOR
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										1.00%
Medium-term Notes | Term Loan due 2022
Debt Instrument [Line Items]
Senior notes face value					$ 150,000,000
Medium-term Notes | Term Loan due 2026
Debt Instrument [Line Items]
Senior notes face value										$ 150,000,000	150,000,000
Weighted average interest rate (LOC)										2.23%
Delayed draw feature period					9 months
Proceeds from draw on term loan			$ 150,000,000
Effective Interest rate										248.00%
Amortization of debt issuance costs										$ 100,000	100,000
Anticipated amount of investment					$ 150,000,000
Payment of up front fees		$ 500,000
Capitalized up front fees		$ 200,000
Debt administration fee								$ 300,000
Unsecured term loan outstanding										150,000,000
Issuance costs										624,000	521,000
Medium-term Notes | Term Loan due 2026 | Interest Rate Swap
Debt Instrument [Line Items]
Derivative notional amount										$ 100,000,000
Medium-term Notes | Term Loan due 2026 | Minimum
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										1.45%
Medium-term Notes | Term Loan due 2026 | Maximum
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										2.40%
Medium-term Notes | Term Loan due 2026 | LIBOR
Debt Instrument [Line Items]
Contractual interest rates, basis spread on variable rate										0.95%
Effective Interest rate										0.95%
Medium-term Notes | Term Loan due 2026 | LIBOR | Minimum
Debt Instrument [Line Items]
Effective Interest rate		0.80%
Medium-term Notes | Term Loan due 2026 | LIBOR | Maximum
Debt Instrument [Line Items]
Effective Interest rate		1.60%
Senior Notes | Senior Notes due 2025
Debt Instrument [Line Items]
Senior notes face value							$ 250,000,000			$ 250,000,000	250,000,000
Effective Interest rate							4.08%
Amortization of debt issuance costs										200,000	200,000	200,000
Deferred finance costs, gross							$ 2,300,000
Issuance costs										$ 882,000	1,124,000
Interest rate on senior notes							3.875%			3.88%
Unaccreted discount							$ 200,000			$ 78,000	100,000
Number of forward starting swaps | swapAgreement							4
Senior Notes | Senior Notes due 2025 | Interest Rate Swap
Debt Instrument [Line Items]
Settlement of swap agreements							$ 1,700,000
Senior Notes | Senior Notes due 2028
Debt Instrument [Line Items]
Senior notes face value										300,000,000	300,000,000			$ 300,000,000
Effective Interest rate														3.84%
Amortization of debt issuance costs										300,000
Deferred finance costs, gross														$ 2,700,000
Issuance costs										$ 1,751,000	2,005,000
Interest rate on senior notes										3.63%				3.625%
Unaccreted discount										$ 1,637,000	1,872,000			$ 2,500,000
Amount of amortization included in interest expense on the Company's consolidated Statements of operations										200,000
Senior Notes | Senior Notes due 2030
Debt Instrument [Line Items]
Senior notes face value				$ 300,000,000						300,000,000	300,000,000
Effective Interest rate				2.71%
Amortization of debt issuance costs										300,000
Deferred finance costs, gross				$ 2,800,000
Issuance costs										$ 2,343,000	2,597,000
Interest rate on senior notes				2.40%						2.40%
Unaccreted discount				$ 1,000,000						$ 844,000	935,000
Amount of amortization included in interest expense on the Company's consolidated Statements of operations										100,000
Senior Notes | Senior Notes due 2031
Debt Instrument [Line Items]
Senior notes face value										300,000,000	300,000,000		$ 300,000,000
Effective Interest rate													2.24%
Amortization of debt issuance costs										200,000
Deferred finance costs, gross													$ 2,800,000
Issuance costs										$ 2,455,000	2,694,000
Interest rate on senior notes										2.05%			2.05%
Unaccreted discount										$ 2,171,000	2,382,000		$ 2,400,000
Amount of amortization included in interest expense on the Company's consolidated Statements of operations										$ 200,000
Mortgage Notes | Minimum
Debt Instrument [Line Items]
Interest rate on senior notes										3.30%
Mortgage Notes | Maximum
Debt Instrument [Line Items]
Interest rate on senior notes										6.20%
Mortgage Notes | Mortgage Notes Payable
Debt Instrument [Line Items]
Senior notes face value										$ 103,664,000	117,221,000
Amortization of debt issuance costs										300,000	200,000	200,000
Issuance costs										651,000	758,000
Unaccreted discount										83,000	150,000
Amortization of debt discount										100,000	400,000	600,000
Amortization of debt premium										500,000	400,000	$ 400,000
Unamortized premium										$ 1,720,000	$ 1,450,000
Mortgage Notes | Mortgage Notes Payable | Minimum
Debt Instrument [Line Items]
Interest rate on senior notes										3.31%
Mortgage Notes | Mortgage Notes Payable | Maximum
Debt Instrument [Line Items]
Interest rate on senior notes										6.17%
Up-front Payment Arrangement | Unsecured Credit Facility
Debt Instrument [Line Items]
Effective Interest rate										1.00%
Remaining borrowing capacity										$ 490,000,000
Up-front Payment Arrangement | Line of Credit | Unsecured Credit Facility
Debt Instrument [Line Items]
Fee amount										3,500,000
Unsecured term loan outstanding										$ 210,000,000