Related Party Transactions (Affiliated Asset Transfers) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Related Party Transaction [Line Items]
Realized investment gains (losses)	$ 89,895	$ (48,635)
Affiliated Entity \| Prudential Insurance February 2019 Sale
Related Party Transaction [Line Items]
Fair Value	4,995
Book Value	5,000
APIC, Net of Tax Increase/(Decrease)	(4)
Realized investment gains (losses)	0
Affiliated Entity \| PALAC April 2019 Sale
Related Party Transaction [Line Items]
Fair Value	14,525
Book Value	13,466
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	1,059
Affiliated Entity \| Term Re September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	9,178
Book Value	8,135
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	1,043
Affiliated Entity \| PURC September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	8,399
Book Value	7,455
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	944
Affiliated Entity \| PARU September 2019 Sale
Related Party Transaction [Line Items]
Fair Value	31,466
Book Value	28,146
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	3,320
Affiliated Entity \| Prudential Insurance September 2019 - Sale
Related Party Transaction [Line Items]
Fair Value	10,702
Book Value	9,254
APIC, Net of Tax Increase/(Decrease)	1,144
Realized investment gains (losses)	0
Affiliated Entity \| PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	7,767
Book Value	6,002
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	1,765
Affiliated Entity \| PAR Term December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	27,330
Book Value	24,739
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	2,591
Affiliated Entity \| PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	93,830
Book Value	75,586
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	18,244
Affiliated Entity \| PURC December 2019 Sale
Related Party Transaction [Line Items]
Fair Value	78,884
Book Value	68,645
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	10,239
Affiliated Entity \| Prudential Insurance December 2019 Purchase
Related Party Transaction [Line Items]
Fair Value	9,000
Book Value	9,000
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	0
Affiliated Entity \| Prudential Insurance March 2020 - Purchase
Related Party Transaction [Line Items]
Fair Value	1,390
Book Value	1,390
APIC, Net of Tax Increase/(Decrease)	0
Realized investment gains (losses)	$ 0

Amortized Cost of assets associated with the Asset Transfer.

No definition available.

Name:	cik777917_AssetTransferAmortizedCost
Namespace Prefix:	cik777917_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair Value of assets associated with the Asset Transfer.

+ References

No definition available.

+ Details

Name:	cik777917_AssetTransferFairValue
Namespace Prefix:	cik777917_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.

+ 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(30)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263

+ Details

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

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PrudentialInsurance1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PALAC3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_TermReMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PurcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_ParuMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_Prudentialinsurance2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PURC2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_ParTermMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PURC3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PURC4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PrudentialInsurance4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cik777917_PrudentialInsurance3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: