Derivative Instruments (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ 8.0
Credit Protection Purchased Notional Amounts	0.0	$ 1.0
Credit Derivative Protection Purchased Fair Value Asset (Liability)	0.0	0.0
Future Policy Benefits
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset (Liability), Net	(8,477.0)	(5,589.0)
Reinsurance Recoverables
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset (Liability), Net	8,486.0	5,600.0
Reinsurance Recoverables \| PALAC and Prudential Insurance
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset (Liability), Net	8,398.0	5,585.0
Reinsurance Recoverables \| Union Hamilton Reinsurance, Ltd.
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset (Liability), Net	88.0	15.0
Policyholders' account balances
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset (Liability), Net	$ (787.0)	$ (13.0)

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=112277219&loc=d3e80748-113994

+ Details

Name:	us-gaap_CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum potential amount of future undiscounted payments that could be required under the credit derivative, before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5708775-113959

+ Details

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

- Definition

Fair value of credit risk derivative asset after deduction of credit risk derivative liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5708775-113959

+ Details

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

- Definition

Net fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as assets, net of those classified as liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

+ Details

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

- Details

Name:	us-gaap_BalanceSheetLocationAxis=cik777917_FuturePolicyBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_ReinsuranceRecoverableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=cik777917_PALACandPrudentialInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=cik777917_UnionHamiltonReinsuranceLtd.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=cik777917_PolicyholdersAccountBalancesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: