XML 77 R51.htm IDEA: XBRL DOCUMENT v2.4.1.9
Senior Notes (Narrative) (Details) (Senior Notes [Member], USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Senior Notes 4.868% [Member]
    
Debt Instrument [Line Items]    
Date issued Jun. 05, 2014  
Principal amounts $ 400,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= cik0000914748_SeniorNotes4868Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt maturity term 30 years  
Debt instrument, stated interest rate 4.868%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= cik0000914748_SeniorNotes4868Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		 4.868%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= cik0000914748_SeniorNotes4868Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember
Maturity Date Jun. 01, 2044 Jun. 01, 2044
Senior Notes 5.4% [Member]
    
Debt Instrument [Line Items]    
Date issued Oct. 12, 2004  
Principal amounts $ 250,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= cik0000914748_SeniorNotes540Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Debt instrument, stated interest rate 5.40%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= cik0000914748_SeniorNotes540Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorNotesMember		  
Maturity Date Oct. 15, 2014