Debt instrument outstanding amount to be paid year and month.

No definition available.

Name:	icon_DebtInstrumentOutstandingAmountToBePaidYearAndMonth
Namespace Prefix:	icon_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the total principal payments made during the annual reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentAnnualPrincipalPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=icon_DeutscheBankAGMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=icon_SeniorNotesFivePointSevenFivePercentDueAugustTwentyTwentyThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleSubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=icon_SeniorNotesOnePointFiveZeroPercentDueMarchTwentyEighteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=icon_SeniorSecuredSecondDelayedDrawTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=icon_VariableFundingNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=icon_SeniorSecuredTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Net Carrying Amount of Debt (Parenthetical) (Detail) - USD ($) $ in Thousands		1 Months Ended
	Aug. 18, 2017	Feb. 28, 2015	Mar. 14, 2018	Feb. 22, 2018	Feb. 12, 2018	Dec. 31, 2017	Oct. 27, 2017	Aug. 02, 2017	Jun. 30, 2017	Dec. 31, 2016	Jul. 31, 2016	Jun. 30, 2016	Mar. 07, 2016	Dec. 31, 2015	Mar. 18, 2013	Nov. 29, 2012
Debt Instrument [Line Items]
Principal amount of long term debt							$ 240,700		$ 0
Deutsche Bank AG
Debt Instrument [Line Items]
Principal amount of long term debt							$ 300,000	$ 300,000
Subsequent Event
Debt Instrument [Line Items]
Aggregate amount of term loan facility				$ 110
5.75% Senior Subordinated Notes Due August 2023 \| Subsequent Event \| Deutsche Bank AG
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage					5.75%
Convertible Notes \| Deutsche Bank AG
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						1.50%
Convertible Notes \| 1.50% Senior Subordinated Notes Due March 15, 2018
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						1.50%				1.50%				1.50%	1.50%
Debt instrument, par value of notes repurchased						$ 58,900				$ 104,900	$ 53,200	$ 51,700
Principal amount of long term debt						236,200									$ 400,000
Convertible Notes \| 1.50% Senior Subordinated Notes Due March 15, 2018 \| Subsequent Event
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage			1.50%	1.50%
Principal amount of long term debt				$ 125,000
Convertible Notes \| 5.75% Senior Subordinated Notes Due August 2023 \| Subsequent Event \| Scenario, Plan
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage				5.75%
Principal amount of long term debt				$ 125,000
Second Delayed Draw Term Loan \| Subsequent Event
Debt Instrument [Line Items]
Aggregate amount of term loan facility			$ 110,000
Variable Funding Notes
Debt Instrument [Line Items]
Principal amount of long term debt						100,000										$ 100,000
Debt Instrument anticipated repayment year and month	2020-01	2018-01
Senior Secured Term Loan
Debt Instrument [Line Items]
Principal amount of long term debt									$ 0				$ 300,000
Debt instrument, annual principal prepayment						$ 28,700				$ 28,700