Debt Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 16, 2018
Debt Instrument [Line Items]
Document Period End Date		Dec. 31, 2019
Derivative, Notional Amount		$ 25,000
Proceeds from Issuance of Long-term Debt		962,000	$ 908,000	$ 1,371,000
Costs associated with loan refinancing or payoff		38,269	31,958	1,549
Long-term Debt, by Maturity [Abstract]
2020		0
2021		0
2022		0
2023		675,000
2024		148,000
Thereafter		2,316,995
Deferred financing costs, net		(37,165)	(33,941)
Total		3,102,830	2,986,054
Interest Expense, Debt [Abstract]
Amortization of deferred financing costs		6,192	5,797	6,167
Credit facility and letter of credit fees		2,265	2,411	2,005
Interest costs capitalized		(4,975)	(9,541)	(9,542)
Interest expense, net		142,002	135,870	133,461
Segment, Continuing Operations [Member]
Interest Expense, Debt [Abstract]
Interest on loans and capital lease obligation		140,697	137,570	135,023
Amortization of deferred financing costs		6,192	5,797	6,167
Interest income		$ (2,177)	(367)	$ (192)
Term loan payable, due February 27, 2023 [Member]
Debt Instrument [Line Items]
Line of credit facility, basis spread on variable rate		1.10%
Debt Instrument, Interest Rate, Effective Percentage		2.81%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		1.10%
Mortgages [Member] | Senior unsecured notes payable, 5.75%, prepaid in full during the three months ended September 30, 2019 (1)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		5.75%
Senior unsecured notes payable [Member]
Debt Instrument [Line Items]
Debt Covenants, Debt to Adjusted Total Assets		60.00%
Debt Covenants, Secured Debt to Adjusted Total Assets		40.00%
Debt Covenants, Debt Service Coverage Ratio		1.5
Debt Covenants, Unencumbered Assets		150.00%
Senior unsecured notes payable [Member] | Senior unsecured note payable, 5.75 percent, due August 15, 2022 [Member]
Debt Instrument [Line Items]
Principal amount of debt tendered		$ 219,400
Debt initial balance		$ 350,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		5.75%
Costs associated with loan refinancing or payoff		$ 1,400
Debt Instrument, Unamortized Premium		38,300
Debt Instrument, Increase, Accrued Interest		$ 600
Senior unsecured notes payable [Member] | Unsecured Revolving Variable Rate Credit Facility, Variable Rate, Due February 27, 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		1.00%
Long-term Debt, by Maturity [Abstract]
Total	[1]	$ 0	30,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 5.75%, prepaid in full during the three months ended September 30, 2019 (1)
Long-term Debt, by Maturity [Abstract]
Total	[2]	$ 0	350,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 5.25%, due July 15, 2023 (3)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		5.25%
Long-term Debt, by Maturity [Abstract]
Total	[3]	$ 275,000	275,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 4.35%, due August 22, 2024 (4)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.35%
Long-term Debt, by Maturity [Abstract]
Total	[4]	$ 148,000	148,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 4.50%, due April 1, 2025 (3)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.50%
Long-term Debt, by Maturity [Abstract]
Total	[3]	$ 300,000	300,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 4.56%, due August 22, 2026 (4)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.56%
Long-term Debt, by Maturity [Abstract]
Total	[4]	$ 192,000	192,000
Senior unsecured notes payable [Member] | Senior unsecured notes payable, 4.75%, due December 15, 2026 (3)
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.75%
Long-term Debt, by Maturity [Abstract]
Total	[3]	$ 450,000	450,000
Senior unsecured notes payable [Member] | Senior Unsecured Notes Payable, 4.50 Percent, Due June 1, 2027 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.50%
Long-term Debt, by Maturity [Abstract]
Total	[3]	$ 450,000	450,000
Senior unsecured notes payable [Member] | Senior Unsecured Notes Payable, 4.95 Percent, Due April 15, 2028 [Member]
Debt Instrument [Line Items]
Debt initial balance		$ 400,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		4.95%			4.95%
Senior unsecured note payable, percentage of principal amount issued		98.883%
Proceeds from Issuance of Long-term Debt		$ 391,800
Long-term Debt, by Maturity [Abstract]
Total	[3],[5]	400,000	400,000
Senior unsecured notes payable [Member] | Senior unsecured note payable, 3.75 percent, due August 15, 2029 [Member]
Debt Instrument [Line Items]
Debt initial balance		$ 500,000
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		3.75%
Senior unsecured note payable, percentage of principal amount issued		99.168%
Long-term Debt, by Maturity [Abstract]
Total	[3],[6]	$ 500,000	0
Line of Credit [Member] | Unsecured Revolving Variable Rate Credit Facility, Variable Rate, Due February 27, 2022 [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 1,000,000
Line of credit facility, basis spread on variable rate		1.00%
Debt Instrument, Interest Rate, Effective Percentage		2.88%
Line of credit facility, amount outstanding		$ 0
Line of Credit Facility, Remaining Borrowing Capacity		1,000,000
Line of Credit [Member] | Combined unsecured revolving credit and term loan facility [Member]
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		1,400,000
Line of credit facility, maximum borrowing capacity		2,400,000
Unsecured term loan [Member] | Term loan payable, due February 27, 2023 [Member]
Long-term Debt, by Maturity [Abstract]
Total	[1]	$ 400,000	400,000
Bond payable, variable rate [Member] | Bonds payable, variable rate, fixed at 1.39% through September 30, 2024, due August 1, 2047
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		1.39%
Long-term Debt, by Maturity [Abstract]
Total		$ 24,995	$ 24,995
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount		400,000
Maximum [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount		400,000
Maximum [Member] | Interest Rate Swap [Member] | Term loan payable, due February 27, 2023 [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount		350,000
Minimum [Member] | Interest Rate Swap [Member] | Term loan payable, due February 27, 2023 [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount		$ 50,000
interest rate swap 3.15percent [Member] | Minimum [Member] | Interest Rate Swap [Member] | Term loan payable, due February 27, 2023 [Member]
Debt Instrument [Line Items]
Derivative, Fixed Interest Rate		3.15%
interest rate swap 3.35 percent [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount		$ 50,000
Derivative, Fixed Interest Rate		3.345%
interest rate swap 3.35 percent [Member] | Maximum [Member] | Interest Rate Swap [Member] | Term loan payable, due February 27, 2023 [Member]
Debt Instrument [Line Items]
Derivative, Fixed Interest Rate		3.35%
Debt Tendered [Member] | Senior unsecured notes payable [Member] | Senior unsecured note payable, 5.75 percent, due August 15, 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium		$ 23,600
Debt Redeemed [Member] | Senior unsecured notes payable [Member] | Senior unsecured note payable, 5.75 percent, due August 15, 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium		$ 13,300

[1] The Company's unsecured revolving credit facility (the facility) bears interest at LIBOR plus 1.00%, which was 2.88% on December 31, 2019. Interest is payable monthly. As of December 31, 2019, the Company had no outstanding balance under the facility and total availability under the facility was $1.0 billion. The Company's unsecured term loan payable bears interest at LIBOR plus 1.10%, which was 2.81% on December 31, 2019. Interest is payable monthly. In addition, there is a $1.0 billion accordion feature on the combined unsecured revolving credit and term loan facility (the combined facility) that increases the maximum borrowing amount available under the combined facility, subject to lender approval, from $1.4 billion to $2.4 billion. If the Company exercises all or any portion of the accordion feature, the resulting increase in the combined facility may have a shorter or longer maturity date and different pricing terms. The combined facility contains financial covenants or restrictions that limit the Company's levels of consolidated debt, secured debt, investment levels outside certain categories and dividend distributions, and require the Company to maintain a minimum consolidated tangible net worth and meet certain coverage levels for fixed charges and debt service.

[2] On August 19, 2019, $219.4 million of the $350.0 million aggregate principal amount of 5.75% Senior Notes due August 15, 2022 were validly tendered and delivered for consideration of the principal amount outstanding plus a premium of $23.6 million. On September 16, 2019, the Company redeemed all of the remaining outstanding notes that were not validly tendered. The notes were redeemed at a price equal to the principal amount outstanding plus a premium calculated pursuant to the terms of the indenture of $13.3 million, together with accrued and unpaid interest of $0.6 million. In connection with the tender offer and the redemption, the Company recorded a non-cash write off of $1.4 million in deferred financing costs. The premiums paid and the non-cash write off, totaling $38.3 million, were recognized as costs associated with loan refinancing or payoff in the accompanying consolidated statements of income and comprehensive income for the year ended December 31, 2019.

[3] These notes contain various covenants, including: (i) a limitation on incurrence of any debt which would cause the ratio of the Company’s debt to adjusted total assets to exceed 60%; (ii) a limitation on incurrence of any secured debt which would cause the ratio of the Company’s secured debt to adjusted total assets to exceed 40%; (iii) a limitation on incurrence of any debt which would cause the Company’s debt service coverage ratio to be less than 1.5 times; and (iv) the maintenance at all times of the Company's total unencumbered assets such that they are not less than 150% of the Company’s outstanding unsecured debt.

[4] These notes (i) contain certain financial and other covenants that generally conform to the combined credit facility described above; (ii) provide investors thereunder certain additional guaranty and lien rights, in the event that certain subsequent events occur; (iii) contain certain "most favored lender" provisions and (iv) impose restrictions on debt that can be incurred by certain subsidiaries of the Company.

[5] On April 16, 2018, the Company issued $400.0 million in aggregate principal amount of senior notes due April 15, 2028, pursuant to an underwritten public offering. The notes bear interest at an annual rate of 4.95%. Interest is payable on April 15 and October 15 of each year beginning on October 15, 2018 until the stated maturity date of April 15, 2028. The notes were issued at 98.883% of their face value and are unsecured. Net proceeds from the note offering of $391.8 million were used to pay down the Company's unsecured revolving credit facility.

[6] On August 15, 2019, the Company issued $500.0 million in aggregate principal amount of senior notes due August 15, 2029 pursuant to an underwritten public offering. The notes bear interest at an annual rate of 3.75%. Interest is payable on February 15 and August 15 of each year beginning on February 15, 2020 until the stated maturity date of August 15, 2029. The notes were issued at 99.168% of their face value and are unsecured. Net proceeds from the note offering were used for the tender offer and redemption of notes due in 2022 discussed above and to pay down the Company's unsecured revolving credit facility.