Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Additional capital lease agreement		$ 884
Rental expenses included in general and administrative expenses	$ 3,200	$ 3,000
Significant liabilities accrued for legal proceedings	0
Contract obligation future minimum non-refundable total payment	70,600
State Tax Authority
Loss Contingencies [Line Items]
Tax examination liability, adjustment from settlement	936
Other Jurisdictions
Loss Contingencies [Line Items]
Tax examination liability, adjustment from settlement	$ 580
Consumer Financial Protection Bureau Litigation Matter
Loss Contingencies [Line Items]
Penalty paid			$ 1,200
Number of plaintiffs | Customer		661
Consumer Financial Protection Bureau Litigation Matter | Subscriber
Loss Contingencies [Line Items]
Refunds paid to certain subscribers		$ 63