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STOCKHOLDERS' EQUITY - Narrative (Detail) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2020 | Mar. 31, 2019 | Jun. 30, 2017
Limited Partners' Capital Account [Line Items] |  |  |
Fair value of stock awards vested | $ 4,979,000 |  |
Stock Options |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Stock-based compensation expense | 0 | $ 0 |
Aggregate intrinsic value of options exercised | 296,000 |  |
Restricted Stock, Restricted Stock Units And Performance Stock Units |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Stock-based compensation expense | 1,515,000 | 1,390,000 |
Restricted Stock |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation expense | $ 45,000 |  |
Restricted Stock | Non Employee Director |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Options, vesting period | 3 years |  |
Restricted Stock Unit |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation expense | $ 5,148,000 |  |
Maximum | Performance Stock Unit |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation expense | $ 7,356,000 |  |
Weighted average | Restricted Stock |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation, weighted average period | 2 years 8 months 12 days |  |
Weighted average | Restricted Stock Unit |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation, weighted average period | 2 years 3 months 18 days |  |
Weighted average | Performance Stock Unit |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Unrecognized stock-based compensation, weighted average period | 2 years 1 month 6 days |  |
2016 Plan |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Options granted, term | 10 years |  |
2016 Plan | Minimum |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Options, vesting period | 1 year |  |
2016 Plan | Maximum |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Options, vesting period | 4 years |  |
Amended and Restated 1997 Employee Stock Purchase Plan |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Stock-based compensation expense | $ 47,000 | $ 41,000 |
Class A Common Stock | 2016 Plan |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Common stock, authorized shares |  |  | 2,250,000
Number of shares available for future grant | 1,121,000 |  |
Class A Common Stock | 2006 Incentive Plan |  |  |
Limited Partners' Capital Account [Line Items] |  |  |
Common stock, additional authorized shares |  |  | 2,723,000

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