Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Detail)

Commitments and Contingencies (Detail) $ in Thousands		1 Months Ended			2 Months Ended	3 Months Ended	4 Months Ended	9 Months Ended	24 Months Ended
Commitments and Contingencies (Detail) $ in Thousands	Apr. 06, 2018 USD ($)	Oct. 31, 2018 USD ($) plaintiff claim	Sep. 30, 2018 USD ($) claim	Nov. 30, 2015 claim	Jan. 31, 2015 USD ($) note_offering claim underwriter	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) claim	Sep. 30, 2018 USD ($)	Dec. 31, 2014 USD ($) security_offering firm underwriter	Dec. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Number of prior note offerings \| note_offering					3
Number of firms that underwrote security offerings \| firm									9
Number of security offerings \| security_offering									6
Loss in period						$ 400		$ 3,393
Loss contingency accrual, product liability			$ 9,100			9,100	$ 9,100	9,100		$ 6,902
Future minimum payments due			$ 68,649			68,649	$ 68,649	68,649
Subsidiaries
Loss Contingencies [Line Items]
Office space lease term											12 years
Estimated annual rent expense											$ 2,000
Ladenburg
Loss Contingencies [Line Items]
Number of underwriters \| underwriter									1
Number of security offerings \| security_offering									2
Securities America
Loss Contingencies [Line Items]
Number of new claims filed \| claim			2				2
Damages sought by plaintiff	$ 5,800
Highland
Loss Contingencies [Line Items]
Future minimum payments due			$ 448			$ 448	$ 448	448
Convertible Notes Payable
Loss Contingencies [Line Items]
Proceeds from issuance Public Offering					$ 300,000
Common Stock
Loss Contingencies [Line Items]
Proceeds from issuance Public Offering					$ 1,656,000
Compensatory damages
Loss Contingencies [Line Items]
Number of new claims filed \| claim				2	2
Number of underwriters \| underwriter					1
Number of plaintiffs \| underwriter					17
Damages sought by plaintiff									$ 151,000
Compensatory damages \| Ladenburg
Loss Contingencies [Line Items]
Damages sought by plaintiff									$ 2,900,000
Compensatory damages \| ARCP July 2013 Offering
Loss Contingencies [Line Items]
Number of underwriters \| underwriter					1
Number of plaintiffs \| underwriter					8
SEC Initiative
Loss Contingencies [Line Items]
Loss in period								$ 2,270
Subsequent Event \| Securities America
Loss Contingencies [Line Items]
Number of plaintiffs \| plaintiff		14
Number of unfiled claims \| claim		1
Damages sought by plaintiff		$ 21,900