Percentage of financial targets to be achieved for participants to receive award.

No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Performance Plan Achievement Percentage

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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Equity-Based Compensation - Restricted Stock Awards with Performance Conditions (Details) - Restricted stock - $ / shares		12 Months Ended
	Mar. 10, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ACTA Stock Price at Issuance (in dollars per share)		$ 14.46	$ 17.96	$ 18.20
Restricted Shares Granted (in shares)		340,566	555,680	581,672
Restricted Shares Vested (in shares)		2,816,884	766,159	785,820
Restricted Shares Forfeited (in shares)		167,712	626,319	70,299
Actua 2015 Performance Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Bonus Potentially Payable in Restricted Stock				150.00%
ACTA Stock Price at Issuance (in dollars per share)				$ 16.76
Restricted Shares Granted (in shares)				316,715
Performance Plan Achievement Percentage				83.00%
Restricted Shares Vested (in shares)				175,249
Restricted Shares Forfeited (in shares)				141,466
Actua 2016 Performance Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Bonus Potentially Payable in Restricted Stock			100.00%
ACTA Stock Price at Issuance (in dollars per share)			$ 8.44
Restricted Shares Granted (in shares)			419,283
Performance Plan Achievement Percentage			60.00%
Restricted Shares Vested (in shares)			251,570
Restricted Shares Forfeited (in shares)			167,713
Actua 2017 Performance Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of Target Bonus Potentially Payable in Restricted Stock		100.00%
ACTA Stock Price at Issuance (in dollars per share)		$ 13.85
Restricted Shares Granted (in shares)	263,756	263,756
Performance Plan Achievement Percentage		100.00%
Restricted Shares Vested (in shares)		263,756
Restricted Shares Forfeited (in shares)		0