Noncontrolling Interests - Holders of Convertible Limited Partnership Units in the Operating Partnership - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling Interests
Noncontrolling Interest [Line Items]
Limited partnership units (in shares)	7,886,916
Limited partnership units, conversion ratio	1
Outstanding stock percent that should be acquired for rights to be exercised	39.90%
Limited partnership units convertible to shares of common stock, eligible for conversion (in shares)	925,000
Fully converted partnership units and diluted weighted average shares outstanding (in shares)	30,900,000	30,200,000	29,500,000
Saul Holdings Limited Partnership
Noncontrolling Interest [Line Items]
Percentage of ownership in operating partnership	74.60%
Saul Holdings Limited Partnership | Noncontrolling Interests
Noncontrolling Interest [Line Items]
Percentage of ownership interest of noncontrolling interest	25.40%