Restructuring - Additional Information (Detail)	1 Months Ended	3 Months Ended			12 Months Ended
	Feb. 29, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) Employee
Restructuring Cost And Reserve [Line Items]
Non-cash impairment charges of long-lived assets		$ 0	$ 7,210,000	$ 1,381,000	$ 1,381,000
Additional cost of goods sold related to inventory					1,229,000
Prepayments to supplier for lower housing assembly			$ 1,024,000		$ 1,024,000
Fair value of inventory	$ 945,000
Inventory impairment charges	$ 945,000
Inventory impairment charges per share | $ / shares	$ 0.05
Severance payment description		Each affected employee received (i) severance payments equal to three months of salary plus an additional amount equal to one week of salary for each year of Alexza service in excess of five years; and (ii) three months of paid medical insurance premiums and outplacement services, or in total, the Severance Package.
Employee Severance [Member]
Restructuring Cost And Reserve [Line Items]
Number of employees eliminated | Employee					33
Employee Severance [Member] | If Employees Position is Not Eliminated [Member]
Restructuring Cost And Reserve [Line Items]
Severance package cost		$ 235,000		$ 0
Aggregate cost of severance package		$ 1,707,000