Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 3,322,599	$ 3,451,149
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	140,254	133,052
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	144,371	1,139,101
Non - credit other - than - temporary Impairments	62	32
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	942	27,298
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	70,611	359,943
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,017	10,897
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,959	38,195
Available-for-sale Securities, Current	3,460,894	3,546,006
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	3,460,894
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	772,214	430,405
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	87	23
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,695	115,374
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	97
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	97
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	772,299	430,331
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,465,967	3,020,744
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	140,167	133,029
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	139,676	1,023,727
Non - credit other - than - temporary Impairments	62	32
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	940	27,201
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	70,611	359,943
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,017	10,897
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,957	38,098
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	2,604,177	3,115,675
Fixed Income Securities [Member] \| Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	312,476	882,631
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	31,106	14,364
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21,593	537,904
Non - credit other - than - temporary Impairments	0	5
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	325	15,878
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	25,981	28,533
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	584	1,198
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	909	17,076
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	342,673	879,919
Fixed Income Securities [Member] \| Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,365,426	1,288,882
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	35,670	6,444
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	22,520	306,506
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	78	8,634
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	34,130	190,273
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	359	8,570
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	437	17,204
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	1,400,659	1,278,122
Fixed Income Securities [Member] \| Foreign Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	30,149	30,496
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	608	399
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	281	1,161
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,061	5,163
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	14	60
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	14	61
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	30,743	30,834
Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	94,211	93,636
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,634	1,371
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	2,833	5,643
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	21	135
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,272	58,495
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	18	478
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	39	613
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	96,806	94,394
Fixed Income Securities [Member] \| Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	211,081	221,825
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	41,241	37,575
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,500	34,852
Non - credit other - than - temporary Impairments	62	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	62	793
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	62	793
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	252,260	258,607
Fixed Income Securities [Member] \| Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	136,547	133,075
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	47	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	83,555	123,848
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	441	1,727
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	441	1,727
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	136,153	131,356
Fixed Income Securities [Member] \| Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	316,077	370,199
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28,861	72,868
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,394	13,813
Non - credit other - than - temporary Impairments	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	13	33
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,167	77,479
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	42	591
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	55	624
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	344,883	442,443
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,238,181
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	140,254
Non - credit other - than - temporary Impairments	62
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,959
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	3,376,476
Collateral Pledged [Member] \| Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	84,418	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0
Non - credit other - than - temporary Impairments	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	84,418	$ 0
Collateral Pledged [Member] \| Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	84,418
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0
Non - credit other - than - temporary Impairments	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0
Fixed income securities, at fair value (amortized cost of $2,465,967 and $3,020,744)	84,418
Asset Pledged as Collateral [Member] \| Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 84,418

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 9A
-URI http://asc.fasb.org/extlink&oid=118954083&loc=SL6284427-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669686-108580

+ Details

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

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

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

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

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

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

+ Details

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

- Definition

Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

+ References

No definition available.

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_CollateralAxis=us-gaap_CollateralPledgedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=us-gaap_AssetPledgedAsCollateralMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: