Pension And Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year $ 516.4    
Fair value of plan assets at end of year 508.4 $ 516.4  
Noncurrent assets 120.5    
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year [1] 345.2    
Service cost [1] 5.3    
Interest cost [1] 12.5    
Plan participants' contributions [1] 0.0    
Actuarial loss (gain) [1] (7.3)    
Benefits paid [1] (23.5)    
Estimated benefits paid by incurred subsidy [1] 0.0    
Defined Benefit Plans, Contributed/Noncontributed Projected Benefit Obligation [1],[2] (4.6)    
Projected benefit obligation at end of year [1] 327.6 345.2  
Fair value of plan assets at beginning of year   304.7  
Fair value of plan assets at beginning of year 304.8    
Actual return on plan assets 0.6    
Employer contributions 16.5    
Defined Benefit Plans, Contributed And Noncontributed Plan Assets [2] (4.0)    
Fair value of plan assets at end of year 294.3 304.8  
Funded Status at end of year (33.3) (40.5)  
Noncurrent assets 0.0    
Current liabilities (0.1)    
Noncurrent liabilities (33.2)    
Net amount recognized at end of year [3] (33.3)    
Unrecognized prior service cost [4] (3.0)    
Unrecognized actuarial loss [4] 130.3    
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability [4] 127.3    
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year [1] 108.9    
Service cost [1] 1.0    
Interest cost [1] 4.0    
Plan participants' contributions [1] 1.6    
Actuarial loss (gain) [1] (11.6)    
Benefits paid [1] (7.5)    
Estimated benefits paid by incurred subsidy [1] 0.2    
Defined Benefit Plans, Contributed/Noncontributed Projected Benefit Obligation [1],[2] (3.2)    
Projected benefit obligation at end of year [1] 93.4 108.9  
Fair value of plan assets at beginning of year 211.6    
Actual return on plan assets (2.0)    
Employer contributions 11.3    
Defined Benefit Plans, Contributed And Noncontributed Plan Assets [2] (1.1)    
Fair value of plan assets at end of year 213.9 211.6  
Funded Status at end of year 120.5    
Noncurrent assets 120.5    
Current liabilities 0.0    
Noncurrent liabilities 0.0    
Net amount recognized at end of year [3] 120.5    
Unrecognized prior service cost [4] 0.1    
Unrecognized actuarial loss [4] (0.4)    
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability [4] (0.3)    
Predecessor      
Defined Benefit Plan Disclosure [Line Items]      
Noncurrent assets   102.7  
Predecessor | Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year [1] 345.2 327.1  
Service cost   4.8 [1] $ 4.8
Interest cost   13.7 [1] 12.6
Plan participants' contributions [1]   0.0  
Actuarial loss (gain) [1]   20.0  
Benefits paid [1]   (20.4)  
Estimated benefits paid by incurred subsidy [1]   0.0  
Defined Benefit Plans, Contributed/Noncontributed Projected Benefit Obligation [1],[2]   0.0  
Projected benefit obligation at end of year [1]   345.2 327.1
Fair value of plan assets at beginning of year 304.7 299.1  
Actual return on plan assets   19.3  
Employer contributions   6.7  
Defined Benefit Plans, Contributed And Noncontributed Plan Assets [2]   0.0  
Fair value of plan assets at end of year   304.7 299.1
Funded Status at end of year   (40.5)  
Noncurrent assets   0.0  
Current liabilities   0.0  
Noncurrent liabilities   (40.5)  
Net amount recognized at end of year [3]   (40.5)  
Unrecognized prior service cost [4]   (4.0)  
Unrecognized actuarial loss [4]   124.5  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability [4]   120.5  
Predecessor | Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year [1] 108.9 105.5  
Service cost   1.1 [1] 1.5
Interest cost   4.6 [1] 4.9
Plan participants' contributions [1]   1.9  
Actuarial loss (gain) [1]   4.6  
Benefits paid [1]   (9.1)  
Estimated benefits paid by incurred subsidy [1]   0.3  
Defined Benefit Plans, Contributed/Noncontributed Projected Benefit Obligation [1],[2]   0.0  
Projected benefit obligation at end of year [1]   108.9 105.5
Fair value of plan assets at beginning of year $ 211.6 198.8  
Actual return on plan assets   9.2  
Employer contributions   10.8  
Defined Benefit Plans, Contributed And Noncontributed Plan Assets [2]   0.0  
Fair value of plan assets at end of year   211.6 $ 198.8
Funded Status at end of year   102.7  
Noncurrent assets   109.8  
Current liabilities   0.0  
Noncurrent liabilities   (7.1)  
Net amount recognized at end of year [3]   102.7  
Unrecognized prior service cost [4]   0.1  
Unrecognized actuarial loss [4]   (8.3)  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability [4]   $ (8.2)  
[1] The change in benefit obligation for Pension Benefits represents the change in Projected Benefit Obligation while the change in benefit obligation for Other Postretirement Benefits represents the change in Accumulated Postretirement Benefit Obligation.
[2] Reflects the removal of amounts related to Crossroads Pipeline Company and CPGSC, which were included in the Predecessor, but were not contributed to the Partnership, as well as the inclusion of CNS Microwave, which was not part of the Predecessor.
[3] The Partnership recognizes in its Consolidated and Combined Balance Sheets the underfunded and overfunded status of its defined benefit postretirement plans, measured as the difference between the fair value of the plan assets and the benefit obligation.
[4] The Partnership determined that the future recovery of pension and other postretirement benefits costs is probable. The Partnership recorded regulatory assets and liabilities of $127.1 million and $0.6 million, respectively, as of December 31, 2015, and $120.9 million and $8.3 million, respectively, as of December 31, 2014 that would otherwise have been recorded to accumulated other comprehensive loss.