Debt (Detail) - Senior Notes [Member] € in Millions, $ in Millions	Jun. 30, 2019 USD ($)	Jun. 30, 2019 EUR (€)
INA Senior Note Due June 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 650	€ 575
Debt Instrument, Interest Rate, Stated Percentage	0.875%	0.875%
Make Whole Premium Additional Percent	0.20%	0.20%
INA Senior Note Due June 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 650	€ 575
Debt Instrument, Interest Rate, Stated Percentage	1.40%	1.40%
Make Whole Premium Additional Percent	0.25%	0.25%
INA Senior Note Due June 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500
Debt Instrument, Interest Rate, Stated Percentage	5.90%	5.90%

Upon election of early redemption, the interest rate percentage in addition to the applicable Treasury Rate which is required to be paid by the Company.

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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- 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.

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