Business Combinations - Pro Forma Results (unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Write-down of deferred tax assets from revaluation of net operating losses due to change in federal tax rate	$ 3,400		$ 3,400
S3
Business Acquisition [Line Items]
Revenue		$ 204,043	203,287
Net income (loss)		$ 2,044	$ (1,456)
Number of shares outstanding - basic (in shares)		12,018	11,881
Number of shares outstanding - diluted (in shares)		13,041	12,873
Basic earnings per share (loss) (in dollars per share)		$ 0.17	$ (0.12)
Diluted earnings per share (loss) (in dollars per share)		$ 0.16	$ (0.11)
Write-down of deferred tax assets from revaluation of net operating losses due to change in federal tax rate			$ 3,400