Credit Facilities (Narrative) (Details)				3 Months Ended	12 Months Ended
	Nov. 12, 2021	Aug. 10, 2020 USD ($)	Mar. 13, 2019 USD ($)	Mar. 31, 2022 USD ($) derivative $ / shares	Dec. 31, 2021 USD ($) $ / shares	Aug. 09, 2020
Line of Credit Facility [Line Items]
Total real estate investments, at cost				$ 2,574,829,000	$ 2,612,660,000
Real estate investment, at cost relating to notes payable				900,000,000
Outstanding balance				501,988,000	$ 502,051,000
Long-term debt, covenant requirements, amount				$ 50,000,000
Effective interest rate				3.06%	3.00%
Long-term debt, covenant requirements, distribution in excess of modified funds from operations, percent		95.00%
Stock repurchase program, maximum authorized amount		$ 50,000,000
Series A Preferred Stock
Line of Credit Facility [Line Items]
Preferred stock, dividend rate, percentage				7.375%	7.375%
Preferred stock, par value (in usd per share) | $ / shares				$ 0.01	$ 0.01
Series B Preferred Stock
Line of Credit Facility [Line Items]
Preferred stock, dividend rate, percentage				7.125%	7.125%
Preferred stock, par value (in usd per share) | $ / shares				$ 0.01	$ 0.01
Commencement Quarter
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity base percent				62.50%
Covenant Period July 1, 2020 through June 30, 2021
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity base percent		67.50%
Covenant Period From July 1, 2021 through Commencement Quarter
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity base percent		65.00%
Covenant Period After Commencement Quarter
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity base percent		62.50%
Covenant Period From April 1, 2021 through June 30, 2021
Line of Credit Facility [Line Items]
Fixed charge coverage ratio		1.00
LIBOR | Commencement Quarter
Line of Credit Facility [Line Items]
Debt instrument, LIBOR floor interest rate		0.25%				0.00%
Unencumbered Properties
Line of Credit Facility [Line Items]
Total real estate investments, at cost				$ 103,900,000
Secured Debt
Line of Credit Facility [Line Items]
Unused borrowing capacity				227,500,000
Credit Facility
Line of Credit Facility [Line Items]
Outstanding balance				$ 147,333,000	$ 147,006,000
Minimum | Covenant Period July 1, 2020 through March 31, 2021
Line of Credit Facility [Line Items]
Fixed charge coverage ratio		1.50
Minimum | Covenant Period From April 1, 2021 through June 30, 2021
Line of Credit Facility [Line Items]
Fixed charge coverage ratio		1.55
Minimum | Covenant Period After June 30, 2021
Line of Credit Facility [Line Items]
Fixed charge coverage ratio	1.50	1.60
Minimum | Covenant Period After November 12, 2021
Line of Credit Facility [Line Items]
Fixed charge coverage ratio				1.50
Minimum | Secured Debt
Line of Credit Facility [Line Items]
Line of credit, increase			$ 370,000,000
Maximum | Secured Debt
Line of Credit Facility [Line Items]
Line of credit, increase			$ 1,000,000,000
Fannie Mae Master Credit Facilities
Line of Credit Facility [Line Items]
Total real estate investments, at cost				$ 600,000,000
Fannie Mae Master Credit Facilities | Credit Facility
Line of Credit Facility [Line Items]
Outstanding balance				354,655,000	355,045,000
New Credit Facilities
Line of Credit Facility [Line Items]
Total real estate investments, at cost				900,000,000
New Credit Facilities | Day Prior to Commencement Quarter
Line of Credit Facility [Line Items]
Long-term debt, covenant requirements, amount				100,000,000
New Credit Facilities | Commencement Quarter
Line of Credit Facility [Line Items]
Long-term debt, covenant requirements, amount		$ 30,000,000
New Credit Facilities | Minimum | Commencement Quarter
Line of Credit Facility [Line Items]
Line of credit facility, current borrowing capacity base percent		55.00%
Term Loan
Line of Credit Facility [Line Items]
Line of credit facility, extension period			1 year
Maximum borrowing capacity			$ 480,000,000
Term Loan | Credit Facility
Line of Credit Facility [Line Items]
Outstanding balance				$ 150,000,000	$ 150,000,000
Effective interest rate				3.98%	4.11%
Term Loan | Minimum | LIBOR | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.55%
Term Loan | Minimum | LIBOR | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.80%
Term Loan | Minimum | Base Rate | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.30%
Term Loan | Minimum | Base Rate | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.55%
Term Loan | Maximum | LIBOR | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.30%
Term Loan | Maximum | LIBOR | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.55%
Term Loan | Maximum | Base Rate | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.05%
Term Loan | Maximum | Base Rate | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.30%
Credit Facility
Line of Credit Facility [Line Items]
Minimum net worth required for compliance		$ 1,200,000
Debt instrument, covenants, percent of net offering proceeds		75.00%
Consolidated tangible net worth				$ 1,500,000
Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 630,000,000
Outstanding balance				$ 0	$ 0
Effective interest rate				0.00%	0.00%
Credit Facility | Minimum | Revolving Credit Facility | LIBOR | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.60%
Credit Facility | Minimum | Revolving Credit Facility | LIBOR | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.85%
Credit Facility | Minimum | Revolving Credit Facility | Base Rate | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.35%
Credit Facility | Minimum | Revolving Credit Facility | Base Rate | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.60%
Credit Facility | Maximum | Revolving Credit Facility | LIBOR | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.35%
Credit Facility | Maximum | Revolving Credit Facility | LIBOR | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.60%
Credit Facility | Maximum | Revolving Credit Facility | Base Rate | Commencement Quarter
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.10%
Credit Facility | Maximum | Revolving Credit Facility | Base Rate | Covenant Period August 10, 2020
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.35%
Interest rate caps | Fannie Mae Master Credit Facilities
Line of Credit Facility [Line Items]
Number of instruments | derivative				9
Notional amount				$ 355,200,000
Interest rate cap				3.50%