Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)		1 Months Ended				3 Months Ended									12 Months Ended
	Jun. 29, 2018 USD ($) property	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Mar. 31, 2017 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) joint_venture property shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment joint_venture property shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Investment [Line Items]
Variable interest entity, number of entities | joint_venture							2								2
Variable interest entity, consolidated, carrying amount, liabilities							$ 56,600,000								$ 56,600,000
Variable interest entity, consolidated, carrying amount, assets							$ 114,800,000								$ 114,800,000
Number of real estate properties (in properties) | property							6								6
Total revenue							$ 86,937,000	$ 85,747,000	$ 91,736,000	$ 89,763,000	$ 88,919,000	$ 87,138,000	$ 92,649,000	$ 90,112,000	$ 354,184,000	$ 358,819,000	$ 354,122,000
Payments to acquire equity method investments															9,973,000	1,400,000	0
Gains on sale of operating properties															$ 3,100,000	$ 5,200,000	$ 3,900,000
Provision for credit losses, net of recoveries as percent of total revenues (as percent)															1.00%	0.80%	0.80%
Weighted average limited partnership units outstanding, basic (in shares) | shares															2,000,000	2,000,000	1,900,000
Antidilutive securities excluded from computation of earnings per share (less than) (in shares) | shares															100,000	100,000	100,000
Number of operating segments | segment															1
Limited partners' capital account, units outstanding (in shares) | shares				1,974,830			2,035,349				1,974,830				2,035,349	1,974,830
Proceeds from sale of real estate															$ 218,387,000	$ 76,075,000	$ 14,187,000
General, administrative, and other															21,320,000	21,749,000	20,603,000
Depreciation and amortization															$ 152,163,000	$ 172,091,000	0
Redeemable Noncontrolling Interests
Investment [Line Items]
Noncontrolling interest, decrease from redemptions or purchase of interests		$ 12,000,000	$ 10,000,000		$ 8,300,000
Capital Unit, Class B
Investment [Line Items]
Number of joint ventures in which units are issued | joint_venture															3
Number of joint ventures in which units are issued, noncontrolling interest | joint_venture															1
Operating Partnership
Investment [Line Items]
Noncontrolling interest, ownership percentage by parent				97.70%			97.60%				97.70%				97.60%	97.70%
Noncontrolling interest, ownership percentage by noncontrolling owners				2.30%			2.40%				2.30%				2.40%	2.30%
Accounting Standards Update 2014-09
Investment [Line Items]
New accounting pronouncement or change in accounting principle, change in revenue (as percent)															1.00%
New accounting pronouncement or change in accounting principle, recognized gains as a percent of revenue (as percent)															1.00%
Fishers Station
Investment [Line Items]
Ownership percentage in equity method investment (as percent)							100.00%								100.00%
Acquisition of partner's interest in Fishers Station operating property					$ 3,800,000
Co-venturer
Investment [Line Items]
Construction loan payable							$ 33,000,000								$ 33,000,000
Co-venturer | Construction Loan
Investment [Line Items]
Debt instrument, face amount				$ 33,800,000.0							$ 33,800,000.0					$ 33,800,000.0
Fee income
Investment [Line Items]
Total revenue															$ 2,523,000	$ 377,000	$ 0
Minimum | Accounting Standards Update 2016-02 | Scenario, Forecast
Investment [Line Items]
Operating lease, right-of-use asset						$ 27,000,000
General, administrative, and other						4,000,000
Depreciation and amortization						(4,000,000)
Maximum | Accounting Standards Update 2016-02 | Scenario, Forecast
Investment [Line Items]
Operating lease, right-of-use asset						32,000,000
General, administrative, and other						5,500,000
Depreciation and amortization						$ (5,500,000)
TH Joint Venture
Investment [Line Items]
Ownership percentage in equity method investment (as percent)	20.00%
Embassy Suites Joint Venture
Investment [Line Items]
Ownership percentage in equity method investment (as percent)				35.00%							35.00%					35.00%
Payments to acquire equity method investments				$ 1,400,000
Embassy Suites Joint Venture | Fee income
Investment [Line Items]
Total revenue																$ 400,000
Building and Improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)															10 years
Building and Improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)															35 years
Equipment and Fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)															5 years
Equipment and Fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life (in years)															10 years
Livingston Shopping Center, Plaza Volente, and Tamiami Crossing
Investment [Line Items]
Proceeds from sale of real estate	$ 89,000,000
Gain on disposal	$ 7,800,000
Livingston Shopping Center, Plaza Volente, and Tamiami Crossing | TH Joint Venture
Investment [Line Items]
Number of real estate properties (in properties) | property	3
Consideration received	$ 99,800,000
Equity method investment	$ 10,000,000