General - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 Segment	Jan. 01, 2019 USD ($)
Schedule Of Accounting Policies [Line Items]
Number of reportable segments | Segment	1
Deferred commission expected amortization period	2 years
ASU 2016-02 [Member] | Subsequent Event [Member]
Schedule Of Accounting Policies [Line Items]
Operating leases, right of use assets		$ 15.0
Operating leases, lease liabilities		$ 15.0
Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Hosting services arrangement period	4 years
Minimum [Member] | Subscriber Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	3 years
Minimum [Member] | Non-competition Agreements [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	2 years
Minimum [Member] | Technology and Other [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	1 year
Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Hosting services arrangement period	5 years
Maximum [Member] | Subscriber Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	10 years
Maximum [Member] | Non-competition Agreements [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	5 years
Maximum [Member] | Technology and Other [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	10 years
Computer Equipment and Software [Member] | Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	2 years
Computer Equipment and Software [Member] | Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	3 years
Office Equipment and Furniture [Member] | Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	5 years
Office Equipment and Furniture [Member] | Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	7 years