Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Detail)

Commitments and Contingencies (Detail)			1 Months Ended			2 Months Ended	3 Months Ended			4 Months Ended	9 Months Ended	24 Months Ended
Commitments and Contingencies (Detail)	Apr. 01, 2017 USD ($)	Mar. 28, 2016 USD ($)	Nov. 30, 2016 USD ($) security_offering	Nov. 30, 2015 claim	Oct. 31, 2013 plaintiff	Jan. 31, 2015 USD ($) note_offering plaintiff claim underwriter	Sep. 30, 2017 USD ($)	Jul. 31, 2017 claim	Jul. 31, 2016 USD ($)	Oct. 31, 2017 USD ($) claim	Sep. 30, 2017 USD ($) claim	Dec. 31, 2014 USD ($) security_offering firm underwriter
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 \| firm												6
Loss contingency accrual, product liability							$ 7,407,000				$ 7,407,000
Loss contingency in period							1,056,000				5,724,000
Future minimum payments due							50,272,000				$ 50,272,000
Reduction of future payments	$ 218,000
Subsidiaries
Loss Contingencies [Line Items]
Office space lease term		12 years
Estimated annual rent expense		$ 1,811,000
Financial penalties due to lease obligation		$ 25,000
Securities America
Loss Contingencies [Line Items]
Number of plaintiffs \| plaintiff					3
Ladenburg
Loss Contingencies [Line Items]
New claims filed, number \| claim								5			5
Number of underwriters \| underwriter												1
Number of security offerings \| security_offering												2
Damages sought by plaintiff									$ 5,500,000
Pending claims, number \| claim								2
Future minimum payments due							3,320,000				$ 3,320,000
Ladenburg \| Subsequent Event
Loss Contingencies [Line Items]
Damages sought by plaintiff										$ 3,000,000
Claims settled, number \| claim										3
Highland
Loss Contingencies [Line Items]
Future minimum payments due							$ 186,000				$ 186,000
Convertible Notes Payable
Loss Contingencies [Line Items]
Proceeds from issuance Public Offering						$ 300,000,000
Common Stock
Loss Contingencies [Line Items]
Proceeds from issuance Public Offering						$ 1,656,000
Compensatory damages
Loss Contingencies [Line Items]
New claims filed, number \| claim				2		2
Number of underwriters \| underwriter						1
Number of plaintiffs \| plaintiff						17
Damages sought by plaintiff												$ 151,000,000
Compensatory damages \| Ladenburg
Loss Contingencies [Line Items]
Number of security offerings \| security_offering			2
Damages sought by plaintiff			$ 105,000,000									$ 2,900,000,000
Compensatory damages \| ARCP July 2013 Offering
Loss Contingencies [Line Items]
Number of underwriters \| underwriter						1
Number of plaintiffs \| plaintiff						8