The amount of estimated time to achieve the milestone.

No definition available.

Name:	CLSN_EstimatedTimeToAchieveTheMilestone
Namespace Prefix:	CLSN_
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Balance Type:	na
Period Type:	duration

- Definition

The amount of gain (loss) from the change in the fair value of earn-out milestone liability.

+ References

No definition available.

+ Details

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Namespace Prefix:	CLSN_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage of risk-adjusted assessment of each milestone.

+ References

No definition available.

+ Details

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Namespace Prefix:	CLSN_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6578-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109124213&loc=d3e6613-128477

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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Earn-out Milestone Liability (Details Narrative) - USD ($)		3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 20, 2014	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Gain (Loss) from Change in Fair Value of Earn out Milestone Liability						$ 547,324
Minimum [Member]
Risk adjusted assessment of each milestone		35.00%	35.00%	50.00%	50.00%	35.00%	50.00%	35.00%	50.00%
Estimated Time to Achieve the Milestone			1 year 29 days		1 year 9 months	9 months 29 days	1 year 6 months	1 year 3 months 29 days	2 years
Maximum [Member]
Risk adjusted assessment of each milestone		80.00%	80.00%	80.00%	80.00%	80.00%	80.00%	80.00%	80.00%
Estimated Time to Achieve the Milestone			1 year 2 months 30 days		2 years 2 months 30 days	1 year	2 years	1 year 6 months	2 years 6 months
EGEN Inc [Member]
Future earn-out payments	$ 30,400,000							$ 24,400,000
Fair value of Acquisition consideration	$ 13,900,000		$ 12,800,000		$ 13,500,000	$ 13,100,000	$ 13,800,000	$ 12,500,000	$ 13,200,000
Gain (Loss) from Change in Fair Value of Earn out Milestone Liability		$ 270,195		$ 292,228		$ 547,324	$ 575,979
EGEN Inc [Member] \| Minimum [Member]
Risk adjusted assessment of each milestone	10.00%
Estimated Time to Achieve the Milestone	1 year 6 months
EGEN Inc [Member] \| Maximum [Member]
Future earn-out payments	$ 30,400,000
Risk adjusted assessment of each milestone	67.00%
Estimated Time to Achieve the Milestone	2 years 6 months