Investments (Analysis of Past Due Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Servicing Liabilities at Fair Value [Line Items]
Current	$ 1,080,864	$ 1,660,599
Total Commercial Mortgage and Other Loans	1,080,864	1,660,886
NonAccrual Status	0	0
30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	287
60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Greater Than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Commercial mortgage loans
Servicing Liabilities at Fair Value [Line Items]
Current	1,017,075	1,545,853
Total Commercial Mortgage and Other Loans	1,017,075	1,545,853
NonAccrual Status	0	0
Commercial mortgage loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Commercial mortgage loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Commercial mortgage loans \| Greater Than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Agricultural property loans
Servicing Liabilities at Fair Value [Line Items]
Current	63,789	106,336
Total Commercial Mortgage and Other Loans	63,789	106,623
NonAccrual Status	0	0
Agricultural property loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	287
Agricultural property loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Agricultural property loans \| Greater Than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Uncollateralized loans
Servicing Liabilities at Fair Value [Line Items]
Current	0	8,410
Total Commercial Mortgage and Other Loans	0	8,410
NonAccrual Status	0	0
Uncollateralized loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Uncollateralized loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Uncollateralized loans \| Greater Than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	$ 0	$ 0

Financing receivables that are current.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

+ Details

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

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

+ Details

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

- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953401-111524

+ Details

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

- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables60To89DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cik777917_CommercialMortgageLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cik777917_AgriculturalPropertyLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=cik777917_UncollateralizedLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: