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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Stock/Unit Based Compensation - Additional Information (Details) - USD ($)			3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 18, 2018	Jan. 12, 2017	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)						1,086,083
Unvested units outstanding (in units)			1,565,629			1,565,629		1,198,703
Weighted average grant date fair value (in dollars per share)						$ 5.95
Vested (in shares)						531,830
Forfeited (in shares)						187,327
2018 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)				45,004	44,198
Vesting period				1 year	1 year	1 year
Weighted average grant date fair value (in dollars per share)				$ 7.67	$ 12
Unrecognized compensation cost			$ 6,077,000			$ 6,077,000
Compensation expense			799,000		$ 1,189,000	$ 1,007,000	$ 1,189,000
Vested (in shares)						31,577
Forfeited (in shares)						12,621
Compensation cost not yet recognized, period for recognition						1 year 11 months 19 days
Options, vested in period, fair value			$ 379,000			$ 5,685,000
2018 Omnibus Incentive Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)			330,628
Vesting period			3 years
Risk-free interest rate			2.29%
Assumed volatility rate			30.00%
2018 Omnibus Incentive Plan \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be issued (in units)			3,006,582			3,006,582
2018 Omnibus Incentive Plan \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)			755,455
Charah Management LLC \| Series C Profits Interests Plan \| Series C Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be issued (in units)			1,000			1,000
Granted in period (in units)								650
Vesting period						5 years
Unvested units outstanding (in units)	540
Allied Power Management, LLC \| Series B Membership Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense			$ 0			$ 0	$ 2,080,000
Allied Power Management, LLC \| Allied Series C Profits Interests Plan \| Allied Series C Profits Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be issued (in units)			1,000			1,000
Granted in period (in units)								550
Compensation expense						$ 0
Predecessor \| Allied Power Management, LLC \| Series B Membership Interests
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense		$ 0
Holders Of Charah Series C Profits Interests And Allied Series C Profits Interests \| IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)	1,215,956
Vested (in shares)	303,993
Holders Of Charah Series C Profits Interests And Allied Series C Profits Interests \| IPO \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares)	911,963
Holders Of Charah Series C Profits Interests And Allied Series C Profits Interests \| IPO \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value (in dollars per share)	$ 12
Vested (in shares)						500,253
Holders Of Charah Series C Profits Interests And Allied Series C Profits Interests \| IPO \| 2018 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)	272,708
Vested (in shares)	68,176
Vesting Over One Year \| 2018 Omnibus Incentive Plan \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)			116,381
Vesting period			1 year
Vesting Over One Year \| Holders Of Charah Series C Profits Interests And Allied Series C Profits Interests \| IPO \| 2018 Omnibus Incentive Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)	204,532
Vesting Over Three Years \| 2018 Omnibus Incentive Plan \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)			550,106
Vesting period			3 years
Vesting Over Four Years \| 2018 Omnibus Incentive Plan \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted in period (in units)			88,968
Vesting period			4 years