Other Assets - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) Property	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Other Assets [Line Items]
Gross carrying amount of intangible assets	$ 21.2	$ 69.5
Number of real estate assets held for sale \| Property	3
Amortization expense related to intangible assets	$ 9.1	$ 6.8	$ 6.5

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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