Real Estate Activities - Gilbert and Florence Facilities - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
Mar. 31, 2017	Dec. 31, 2018
Business Acquisition [Line Items]
Gain offset by non-cash charges	$ 0.6
Gilbert and Florence Facilities [Member]
Business Acquisition [Line Items]
Gain offset by non-cash charges		$ 1.1
Gilbert and Florence Facilities [Member] \| Total Gross Assets [Member] \| Credit Concentration Risk [Member]
Business Acquisition [Line Items]
Percentage of Total Gross Assets		0.20%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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