Investment in Joint Ventures - Company's Share of Unconsolidated Joint Ventures' Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ 1,221	$ 1,116
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	654	922
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	332	455
Other Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ 235	$ (261)