Stockholders' Equity - Equity Issuances (Details)		1 Months Ended		9 Months Ended	12 Months Ended
	Sep. 14, 2016 USD ($) clinical_trial_subject $ / shares	Feb. 28, 2018 USD ($) shares	Nov. 30, 2015 USD ($) shares	Sep. 30, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 shares	Aug. 31, 2018 USD ($) shares
Class of Stock [Line Items]
Shares issued, price (in usd per share) | $ / shares	$ 4.72
Private Purchase Agreement [Member]
Class of Stock [Line Items]
Proceeds from issuance of common stock, initial closing	$ 6,600,000
Proceeds from issuance of common stock, second closing					$ 4,400,000
Stock issued (shares) | shares					900,000	1,400,000
Number of subjects for Phase 2 CLBS03 clinical trial, second closing | clinical_trial_subject	70
Aspire Capital Purchase Agreement [Member]
Class of Stock [Line Items]
Stock issued (shares) | shares			319,776
Proceeds from issuance of stock			$ 1,500,000
Purchase commitment, remaining minimum amount committed			$ 30,000,000
Purchase commitment, maximum amount committed (shares) | shares			1,100,000
Term of agreement in months			24 months
H.C. Wainwright Sales Agreement [Member]
Class of Stock [Line Items]
Stock issued (shares) | shares				149,041
Proceeds from issuance of stock				$ 1,000,000
Aggregate offering amount authorized per agreement		$ 12,000,000
Maximum number of shares authorized per agreement | shares		2,790,697					4,921,260
Commission on gross proceeds due to third party (percent)		3.00%
H.C. Wainwright Sales Amended Agreement [Member]
Class of Stock [Line Items]
Aggregate offering amount authorized per agreement							$ 25,000,000