XML 11 R39.htm IDEA: XBRL DOCUMENT v3.3.0.814
Long-Term Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Detail) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Long-term Debt, Current and Noncurrent Abstract    
Less: current maturities $ (19,865) $ (19,192)
Long-term debt, less current maturities 1,540,364 1,637,592
Carrying Amount [Member]    
Debt Instrument [Line Items]    
Total long-term debt 1,560,229 1,656,784
Long-term Debt, Current and Noncurrent Abstract    
Less: current maturities (19,865) (19,192)
Long-term debt, less current maturities 1,540,364 1,637,592
Total long-term debt 1,560,229 1,656,784
Carrying Amount [Member] | IDRBs [Member]    
Debt Instrument [Line Items]    
Unsecured debt 323,316 374,112
Carrying Amount [Member] | Centuri secured revolving credit and term loan facility [Member]    
Debt Instrument [Line Items]    
Centuri secured revolving credit and term loan facility 208,787 199,267
Carrying Amount [Member] | Centuri other debt obligations [Member]    
Debt Instrument [Line Items]    
Centuri other debt obligations 28,583 31,128
Carrying Amount [Member] | Debentures [Member]    
Debt Instrument [Line Items]    
Unamortized discount (4,957) (5,223)
Notes payable 902,543 902,277
Carrying Amount [Member] | Debentures [Member] | Notes, 4.45%, due 2020 [Member]    
Debt Instrument [Line Items]    
Notes payable 125,000 125,000
Carrying Amount [Member] | Debentures [Member] | Notes, 6.1%, due 2041 [Member]    
Debt Instrument [Line Items]    
Notes payable 125,000 125,000
Carrying Amount [Member] | Debentures [Member] | Notes, 3.875%, due 2022 [Member]    
Debt Instrument [Line Items]    
Notes payable 250,000 250,000
Carrying Amount [Member] | Debentures [Member] | Notes, 4.875%, due 2043 [Member]    
Debt Instrument [Line Items]    
Notes payable 250,000 250,000
Carrying Amount [Member] | Debentures [Member] | 8% Series, due 2026 [Member]    
Debt Instrument [Line Items]    
Notes payable 75,000 75,000
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.59% series, due 2017 [Member]    
Debt Instrument [Line Items]    
Notes payable 25,000 25,000
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.78% series, due 2022 [Member]    
Debt Instrument [Line Items]    
Notes payable 25,000 25,000
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.92% series, due 2027 [Member]    
Debt Instrument [Line Items]    
Notes payable 25,000 25,000
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 6.76% series, due 2027 [Member]    
Debt Instrument [Line Items]    
Notes payable 7,500 7,500
Carrying Amount [Member] | Debentures [Member] | Revolving credit facility and commercial paper [Member]    
Debt Instrument [Line Items]    
Line of credit facility 97,000 150,000
Carrying Amount [Member] | Variable-rate bonds [Member] | Tax-exempt Series A, due 2028 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 50,000 50,000
Carrying Amount [Member] | Variable-rate bonds [Member] | 2003 Series A, due 2038 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 50,000 50,000
Carrying Amount [Member] | Variable-rate bonds [Member] | 2008 Series A, due 2038 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 50,000 50,000
Carrying Amount [Member] | Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 50,000 50,000
Carrying Amount [Member] | Fixed-rate bonds [Member]    
Debt Instrument [Line Items]    
Unamortized discount (1,539) (1,943)
Carrying Amount [Member] | Fixed-rate bonds [Member] | 5.25% 2003 Series D, due 2038 [Member]    
Debt Instrument [Line Items]    
Unsecured debt   20,000
Carrying Amount [Member] | Fixed-rate bonds [Member] | 5.00% 2004 Series B, due 2033 [Member]    
Debt Instrument [Line Items]    
Unsecured debt   31,200
Carrying Amount [Member] | Fixed-rate bonds [Member] | 4.85% 2005 Series A, due 2035 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 100,000 100,000
Carrying Amount [Member] | Fixed-rate bonds [Member] | 4.75% 2006 Series A, due 2036 [Member]    
Debt Instrument [Line Items]    
Unsecured debt 24,855 24,855
Market Value [Member] | Centuri secured revolving credit and term loan facility [Member]    
Debt Instrument [Line Items]    
Centuri secured revolving credit and term loan facility 209,213 200,341
Market Value [Member] | Centuri other debt obligations [Member]    
Debt Instrument [Line Items]    
Centuri other debt obligations 28,868 31,127
Market Value [Member] | Debentures [Member] | Notes, 4.45%, due 2020 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 132,769 133,403
Market Value [Member] | Debentures [Member] | Notes, 6.1%, due 2041 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 147,451 157,290
Market Value [Member] | Debentures [Member] | Notes, 3.875%, due 2022 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 263,023 262,030
Market Value [Member] | Debentures [Member] | Notes, 4.875%, due 2043 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 266,370 280,903
Market Value [Member] | Debentures [Member] | 8% Series, due 2026 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 99,380 102,296
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.59% series, due 2017 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 26,662 27,573
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.78% series, due 2022 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 30,621 31,144
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.92% series, due 2027 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 32,726 33,695
Market Value [Member] | Debentures [Member] | Medium-term notes, 6.76% series, due 2027 [Member]    
Debt Instrument [Line Items]    
Notes payable, fair value disclosure 8,917 9,156
Market Value [Member] | Debentures [Member] | Revolving credit facility and commercial paper [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 97,000 150,000
Market Value [Member] | Variable-rate bonds [Member] | Tax-exempt Series A, due 2028 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 50,000 50,000
Market Value [Member] | Variable-rate bonds [Member] | 2003 Series A, due 2038 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 50,000 50,000
Market Value [Member] | Variable-rate bonds [Member] | 2008 Series A, due 2038 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 50,000 50,000
Market Value [Member] | Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 50,000 50,000
Market Value [Member] | Fixed-rate bonds [Member] | 5.25% 2003 Series D, due 2038 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 0 20,277
Market Value [Member] | Fixed-rate bonds [Member] | 5.00% 2004 Series B, due 2033 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 0 31,223
Market Value [Member] | Fixed-rate bonds [Member] | 4.85% 2005 Series A, due 2035 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value 100,415 100,071
Market Value [Member] | Fixed-rate bonds [Member] | 4.75% 2006 Series A, due 2036 [Member]    
Debt Instrument [Line Items]    
Line of credit facility, fair value $ 25,089 $ 25,399