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

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

- 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_LongtermDebtTypeAxis=icon_VariableFundingNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Schedule of Debt Obligations (Parenthetical) (Detail) - USD ($) $ in Millions		1 Months Ended
	Aug. 18, 2017	Feb. 28, 2015	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jul. 31, 2016	Jun. 30, 2016	Mar. 18, 2013	May 23, 2011
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%	2.50%
Debt instrument, par value of notes repurchased			$ 58.9	$ 104.9		$ 53.2	$ 51.7
Variable Funding Notes
Debt Instrument [Line Items]
Debt Instrument anticipated repayment year and month	2020-01	2018-01