Shareholders' Equity - Summary of Outstanding Warrants for Company's Common Stock (Detail)	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	2,066,645
Exercise Price One [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	401,391
Exercise Price | $ / shares	$ 45.50
Expiration Date	2018-06
Exercise Price Two [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	314,446
Exercise Price | $ / shares	$ 52.50
Expiration Date	2019-11
Exercise Price Three [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	32,467
Exercise Price | $ / shares	$ 7.00
Expiration Date	2020-08
Exercise Price Four [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	403,927
Exercise Price | $ / shares	$ 29.40
Expiration Date	2021-02
Exercise Price Five [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	72,953
Exercise Price | $ / shares	$ 8.98
Expiration Date	2021-06
Exercise Price Six [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	24,725
Exercise Price | $ / shares	$ 9.10
Expiration Date	2027-04
Exercise Price Seven [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	41,736
Exercise Price | $ / shares	$ 5.39
Expiration Date	2027-06
Exercise Price Eight [Member]
Class of Warrant or Right [Line Items]
Shares Underlying Outstanding Warrants	775,000
Exercise Price | $ / shares	$ 0.01
Expiration Date	2024-10