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Leases - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019
Maximum [Member]
Leases [Line Items]
Operating and finance leases, remaining lease terms	11 years
Minimum [Member]
Leases [Line Items]
Operating and finance leases, remaining lease terms	1 year

X

- Definition

Leases.

+ References

No definition available.

+ Details

Name:	iosp_LeasesLineItems
Namespace Prefix:	iosp_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Lessee, operating and finance leases remaining lease term.

+ References

No definition available.

+ Details

Name:	iosp_LesseeOperatingAndFinanceLeasesRemainingLeaseTerm
Namespace Prefix:	iosp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: