XML 94 R77.htm IDEA: XBRL DOCUMENT v3.20.4

Investment Information - Aging of Available For Sale Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands		Dec. 31, 2020		Dec. 31, 2019
Available for sale securities:
Estimated Fair Value - Less than 12 Months		$ 3,788,763		$ 4,280,273
Gross Unrealized Losses - Less than 12 Months		(76,067)		(52,926)
Estimated Fair Value - 12 Months or More		70,404		158,538
Gross Unrealized Losses - 12 Months or More		(3,587)		(2,077)
Estimated Fair Value - Total		3,859,167		4,438,811
Gross Unrealized Losses - Total		(79,654)		(55,003)
Fixed maturities and fixed maturities pledged under securities lending agreements
Available for sale securities:
Estimated Fair Value - Less than 12 Months		3,690,843	[1]	4,184,496
Gross Unrealized Losses - Less than 12 Months		(74,004)	[1]	(51,378)
Estimated Fair Value - 12 Months or More		70,404	[1]	158,538
Gross Unrealized Losses - 12 Months or More		(3,587)	[1]	(2,077)
Estimated Fair Value - Total		3,761,247	[1]	4,343,034
Gross Unrealized Losses - Total		(77,591)	[1]	(53,455)
Fixed maturities and fixed maturities pledged under securities lending agreements | Corporate bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	747,442		675,131
Gross Unrealized Losses - Less than 12 Months	[1]	(33,086)		(12,350)
Estimated Fair Value - 12 Months or More	[1]	3,934		37,671
Gross Unrealized Losses - 12 Months or More	[1]	(1,302)		(443)
Estimated Fair Value - Total	[1]	751,376		712,802
Gross Unrealized Losses - Total	[1]	(34,388)		(12,793)
Fixed maturities and fixed maturities pledged under securities lending agreements | Mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	284,619		102,887
Gross Unrealized Losses - Less than 12 Months	[1]	(4,788)		(927)
Estimated Fair Value - 12 Months or More	[1]	3,637		203
Gross Unrealized Losses - 12 Months or More	[1]	(240)		(4)
Estimated Fair Value - Total	[1]	288,256		103,090
Gross Unrealized Losses - Total	[1]	(5,028)		(931)
Fixed maturities and fixed maturities pledged under securities lending agreements | Municipal bonds
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	67,937		220,296
Gross Unrealized Losses - Less than 12 Months	[1]	(3,835)		(2,213)
Estimated Fair Value - 12 Months or More	[1]	0		0
Gross Unrealized Losses - 12 Months or More	[1]	0		0
Estimated Fair Value - Total	[1]	67,937		220,296
Gross Unrealized Losses - Total	[1]	(3,835)		(2,213)
Fixed maturities and fixed maturities pledged under securities lending agreements | Commercial mortgage backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	126,624		147,290
Gross Unrealized Losses - Less than 12 Months	[1]	(2,916)		(2,302)
Estimated Fair Value - 12 Months or More	[1]	2,655		2,683
Gross Unrealized Losses - 12 Months or More	[1]	(38)		(28)
Estimated Fair Value - Total	[1]	129,279		149,973
Gross Unrealized Losses - Total	[1]	(2,954)		(2,330)
Fixed maturities and fixed maturities pledged under securities lending agreements | US government and government agencies
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	1,285,907		1,373,127
Gross Unrealized Losses - Less than 12 Months	[1]	(12,611)		(10,089)
Estimated Fair Value - 12 Months or More	[1]	0		32,058
Gross Unrealized Losses - 12 Months or More	[1]	0		(45)
Estimated Fair Value - Total	[1]	1,285,907		1,405,185
Gross Unrealized Losses - Total	[1]	(12,611)		(10,134)
Fixed maturities and fixed maturities pledged under securities lending agreements | Non-US government securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	543,844		1,224,243
Gross Unrealized Losses - Less than 12 Months	[1]	(7,658)		(20,163)
Estimated Fair Value - 12 Months or More	[1]	2,441		37,610
Gross Unrealized Losses - 12 Months or More	[1]	(402)		(167)
Estimated Fair Value - Total	[1]	546,285		1,261,853
Gross Unrealized Losses - Total	[1]	(8,060)		(20,330)
Fixed maturities and fixed maturities pledged under securities lending agreements | Asset backed securities
Available for sale securities:
Estimated Fair Value - Less than 12 Months	[1]	634,470		441,522
Gross Unrealized Losses - Less than 12 Months	[1]	(9,110)		(3,334)
Estimated Fair Value - 12 Months or More	[1]	57,737		48,313
Gross Unrealized Losses - 12 Months or More	[1]	(1,605)		(1,390)
Estimated Fair Value - Total	[1]	692,207		489,835
Gross Unrealized Losses - Total	[1]	(10,715)		(4,724)
Short-term investments
Available for sale securities:
Estimated Fair Value - Less than 12 Months		97,920		95,777
Gross Unrealized Losses - Less than 12 Months		(2,063)		(1,548)
Estimated Fair Value - 12 Months or More		0		0
Gross Unrealized Losses - 12 Months or More		0		0
Estimated Fair Value - Total		97,920		95,777
Gross Unrealized Losses - Total		$ (2,063)		$ (1,548)
[1] In securities lending transactions, the Company receives collateral in excess of the fair value of the fixed maturities pledged. For purposes of this table, the Company has excluded the collateral received under securities lending, at fair value and included the securities pledged under securities lending, at fair value. See “—Securities Lending Agreements.”

X

- References

No definition available.

+ Details

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

X

- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale in a continuous loss position.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27337-111563

+ Details

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

X

- Definition

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

No definition available.

+ Details

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

X

- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for twelve months or longer.

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=acgl_NonUsGovernmentSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: