Notes Payable (Unsecured Senior Notes) (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) tranche	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 1,939,743,000	$ 2,218,093,000
Unsecured Senior Notes
Debt Instrument [Line Items]
Debt amount	$ 1,000,000,000.0
Number of tranches | tranche	5
Minimum fixed charge coverage ratio	1.50
Unsecured Senior Notes | Minimum
Debt Instrument [Line Items]
Minimum unencumbered interest coverage ratio	1.75
Unsecured Senior Notes | Maximum
Debt Instrument [Line Items]
Leverage ratio (percent)	60.00%
Secured leverage ratio (percent)	40.00%
Unsecured Senior Notes | 4.09% Senior Notes, Unsecured
Debt Instrument [Line Items]
Debt amount	$ 100,000,000
Long-term debt	$ 100,000,000	100,000,000
Interest rate	4.09%
Unsecured Senior Notes | 3.91% Senior Notes, Unsecured
Debt Instrument [Line Items]
Debt amount	$ 250,000,000
Long-term debt	$ 250,000,000	250,000,000
Interest rate	3.91%
Unsecured Senior Notes | 3.78% Senior Notes, Unsecured
Debt Instrument [Line Items]
Debt amount	$ 125,000,000
Long-term debt	$ 125,000,000	125,000,000
Interest rate	3.78%
Unsecured Senior Notes | 3.86% Senior Notes, Unsecured
Debt Instrument [Line Items]
Debt amount	$ 250,000,000
Long-term debt	$ 250,000,000	250,000,000
Interest rate	3.86%
Unsecured Senior Notes | 3.95% Senior Notes, Unsecured
Debt Instrument [Line Items]
Debt amount	$ 275,000,000
Long-term debt	$ 275,000,000	$ 275,000,000
Interest rate	3.95%