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	15 Months Ended	24 Months Ended
Commitments and Contingencies (Detail)	Apr. 06, 2018 USD ($)	Mar. 28, 2016 USD ($)	Nov. 30, 2015 claim	Jan. 31, 2015 USD ($) note_offering plaintiff claim underwriter	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Oct. 31, 2017 USD ($) claim	Jul. 31, 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					$ 8,821,000	$ 6,902,000
Loss in Period					2,572,000	$ 143,000
Future minimum payments due					71,926,000
Subsidiaries
Loss Contingencies [Line Items]
Office space lease term		12 years
Estimated annual rent expense		$ 2,000,000
Ladenburg
Loss Contingencies [Line Items]
New claims filed, number \| claim								5
Number of underwriters \| underwriter									1
Number of security offerings \| security_offering									2
Damages sought by plaintiff							$ 300,000
Claims settled, number \| claim							4
Highland
Loss Contingencies [Line Items]
Future minimum payments due					$ 183,000
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								$ 5,400,000	$ 151,000,000
Compensatory damages \| Ladenburg
Loss Contingencies [Line Items]
Damages sought by plaintiff									$ 2,900,000,000
Compensatory damages \| ARCP July 2013 Offering
Loss Contingencies [Line Items]
Number of underwriters \| underwriter				1
Number of plaintiffs \| plaintiff				8
Subsequent Event \| Securities America
Loss Contingencies [Line Items]
Damages sought by plaintiff	$ 5,800,000