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.

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill		$ 68.5
Amortization of intangible asset		3.1	$ 2.0
Commercial [Member]
Goodwill [Line Items]
Goodwill		54.3
Residential [Member]
Goodwill [Line Items]
Goodwill		$ 14.2
Domain Names [Member]
Goodwill [Line Items]
Amortization period		15 years
Purchase of domain names	$ 6.3
Customer Backlog [Member]
Goodwill [Line Items]
Amortization period		12 months
Trade Names and Trademarks [Member]
Goodwill [Line Items]
Amortization period		12 months