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As of the balance sheet date, the projected compensation cost in remaining period of current year for equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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As of the balance sheet date, the projected compensation cost in fifth fiscal year of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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As of the balance sheet date, the projected compensation cost in fourth fiscal year of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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As of the balance sheet date, the projected compensation cost in sixth fiscal year of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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As of the balance sheet date, the projected compensation cost in third fiscal year of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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As of the balance sheet date, the projected compensation cost in second fiscal year of equity-based awards made to employees under equity-based compensation awards that have yet to vest.

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No definition available.

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Number of stock award and incentive plan approved by shareholders to provide incentive to key individuals.

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No definition available.

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Number of shares of common stock issued for each share of common stock the parent company in a spin-off.

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No definition available.

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Number of votes per share entitled to class of shares.

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Aggregate number of common shares reserved for future issuance.

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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Additional share-based compensation cost recognized as a result of an occurrence of an event that accelerates its recognition.

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No definition available.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Number of shares for which recognition of compensation cost was accelerated.

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Percentage of vesting of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stockholders' Equity, Voting Rights, Stock Award and Incentive Plan (Details) $ / shares in Units, $ in Thousands				3 Months Ended						6 Months Ended		12 Months Ended
	Apr. 04, 2018 $ / shares shares	Jan. 05, 2018 shares	Nov. 30, 2015 shares	Jun. 30, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($) $ / shares shares	Mar. 31, 2017 USD ($)	Jun. 30, 2018 USD ($) VoteperShare Plan $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Stock Award and Incentive Plan [Abstract]
Number of incentive plans \| Plan										1
Compensation record expenses due to accelerated vesting				$ 200						$ 200
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
Actual stock based compensation expense				351	$ 187	$ 1,488	$ 369	$ 4,381	$ 699	541	$ 5,078	$ 6,937
2017				1,240						1,240
2019				1,404						1,404
2020				1,404						1,404
2021				957						957
2022				808						808
2023				202						202
Employee Service Share-based Compensation, Aggregate Disclosures [Abstract]
Compensation cost related to non-vested options not yet recognized				$ 5,500						$ 5,500
Stock Options [Member] \| Maximum [Member]
Stock Award and Incentive Plan [Abstract]
Term of nonqualified stock options										10 years
Restricted Stock Awards [Member]
Stock Award and Incentive Plan [Abstract]
RSAs granted (in shares) \| shares	270,500
Grant date fair value (in dollars per share) \| $ / shares	$ 24.77
RSA shares outstanding (in shares) \| shares				268,500		19,400		420,240		268,500	420,240	19,400
Average weighted grant price (in dollars per share) \| $ / shares				$ 24.77		$ 65.67		$ 65.59		$ 24.77	$ 65.59	$ 65.67
Number of shares with accelerated vesting (in shares) \| shares		19,400
Restricted Stock Awards [Member] \| ASU 2016-09 [Member]
Stock Award and Incentive Plan [Abstract]
Tax benefit from stock based compensation expenses				$ 100						$ 0
Restricted Stock Awards [Member] \| Vesting in Three Years from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										30.00%
Award vesting period										3 years
Restricted Stock Awards [Member] \| Vesting in Five Years from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										70.00%
Award vesting period										5 years
Restricted Stock Awards [Member] \| Vesting in Year Four from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Five from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Six from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Seven from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Eight from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Nine from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| Vesting in Year Ten from Date of Grant [Member]
Stock Award and Incentive Plan [Abstract]
Award vesting percentage										10.00%
Restricted Stock Awards [Member] \| AC [Member]
Stock Award and Incentive Plan [Abstract]
Compensation record expenses due to accelerated vesting				0						$ 0
Q1 [Member]
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
2019				351						351
2020				351						351
2021				351						351
2022				202						202
2023				202						202
Q2 [Member]
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
2019				351						351
2020				351						351
2021				202						202
2022				202						202
2023				0						0
Q3 [Member]
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
2017				351						351
2019				351						351
2020				351						351
2021				202						202
2022				202						202
2023				0						0
Q4 [Member]
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
2017				351						351
2019				351						351
2020				351						351
2021				202						202
2022				202						202
2023				$ 0						$ 0
Class A [Member]
Voting Rights [Abstract]
Number of votes per share \| VoteperShare										1
Class A [Member] \| Maximum [Member]
Stock Award and Incentive Plan [Abstract]
Number of shares reserved for issuance under each plan (in shares) \| shares				7,500,000						7,500,000
Class A [Member] \| Restricted Stock Awards [Member] \| AC [Member]
Stock Award and Incentive Plan [Abstract]
Number of shares of common stock issued for each share of Gamco common stock in spin-off (in shares) \| shares			1
Class B [Member]
Voting Rights [Abstract]
Number of votes per share \| VoteperShare										10