Nature of Business and Financial Statement Presentation - Additional Information (Detail) $ / shares in Units, $ in Millions	3 Months Ended				9 Months Ended
	Mar. 31, 2020 $ / shares	Sep. 30, 2019 $ / shares	Jun. 30, 2019 $ / shares	Mar. 31, 2019 $ / shares	Sep. 30, 2020 USD ($) JointVenture	Dec. 31, 2019 USD ($)
Nature Of Business And Financial Statement Presentation [Line Items]
Maximum exposure to losses associated with VIEs | $					$ 96.7	$ 114.0
Common share dividend declared per share | $ / shares	$ 0.20	$ 0.20	$ 0.20	$ 0.20
Accounting Standards Update [Extensible List]					us-gaap:AccountingStandardsUpdate201613Member
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]					true
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]					true
Variable Interest Entity, Not Primary Beneficiary [Member]
Nature Of Business And Financial Statement Presentation [Line Items]
Number of unconsolidated joint ventures | JointVenture					2