Notes Payable - Unsecured Notes and Term Loans Outstanding (Details) - USD ($)		12 Months Ended
		Dec. 31, 2019	Nov. 30, 2019	Dec. 31, 2018
Unsecured Debt
Debt Instrument [Line Items]
Total principal		$ 1,000,000,000		$ 1,000,000,000
Premiums and discounts, net		(797,000)		(1,189,000)
Deferred issuance costs, net		(2,481,000)		(3,414,000)
Total, net		996,722,000		995,397,000
Principal amounts due		$ 0
10 Year Unsecured Notes 4.95%
Debt Instrument [Line Items]
Coupon/Stated rate (percent)			4.95%
10 Year Unsecured Notes 4.95% | Unsecured Debt
Debt Instrument [Line Items]
Coupon/Stated rate (percent)		4.95%
Effective interest rate (percent)	[1]	5.05%
Total principal		$ 250,000,000		250,000,000
Payoff Date/Maturity Date	[2]	Oct. 01, 2020
2015 Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Effective interest rate (percent)	[1]	2.72%
Total principal		$ 150,000,000		150,000,000
Payoff Date/Maturity Date	[2]	Mar. 15, 2021
2015 Term Loan | Unsecured Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (percent)		1.10%
10 Year Unsecured Notes 3.95% | Unsecured Debt
Debt Instrument [Line Items]
Coupon/Stated rate (percent)		3.95%
Effective interest rate (percent)	[1]	4.02%
Total principal		$ 300,000,000		300,000,000
Payoff Date/Maturity Date	[2]	Oct. 15, 2022
2018 Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Effective interest rate (percent)	[1],[3]	2.87%
Total principal	[3]	$ 250,000,000		250,000,000
Payoff Date/Maturity Date	[2]	Jul. 21, 2023
2018 Term Loan | Unsecured Debt | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (percent)		1.10%
30 Year Unsecured Notes 7.25% | Unsecured Debt
Debt Instrument [Line Items]
Coupon/Stated rate (percent)		7.25%
Effective interest rate (percent)	[1]	7.36%
Total principal		$ 50,000,000		$ 50,000,000
Payoff Date/Maturity Date	[2]	Feb. 25, 2028

[1] For fixed rate notes, the effective rate represents the yield on issuance date, including the effects of discounts on the notes. For variable rate notes, the effective rate represents the rate as fixed by interest rate derivatives (see note 8).

[2] No principal amounts are due prior to maturity.

[3] The 2018 Term Loan increased and replaced the 2016 Term Loan (see note 6).