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Derivative Instruments, Hedging Activities and Fair Value Measurements
6 Months Ended
Jun. 30, 2018
Derivative Instruments, Hedging Activities and Fair Value Measurements [Abstract]  
Derivative Instruments, Hedging Activities and Fair Value Measurements
Note 14.  Derivative Instruments, Hedging Activities and Fair Value Measurements

In the normal course of our business operations, we are exposed to certain risks, including changes in interest rates and commodity prices.  In order to manage risks associated with assets, liabilities and certain anticipated future transactions, we use derivative instruments such as futures, forward contracts, swaps, options and other instruments with similar characteristics.  Substantially all of our derivatives are used for non-trading activities.

On January 1, 2018, we early adopted ASU 2017-12, Derivatives and Hedging (Topic 815):  Targeted Improvements to Accounting for Hedging Activities.  Since the impact of the new guidance was not material to our consolidated financial statements, no transition adjustments were recorded. In accordance with ASU 2017-12 both the effective and ineffective portion of a cash flow hedge will be initially reported as a component of accumulated other comprehensive income (loss) and reclassified into earnings when the forecasted transaction affects earnings.

Interest Rate Hedging Activities
We may utilize interest rate swaps, forward starting swaps and similar derivative instruments to manage our exposure to changes in interest rates charged on borrowings under certain consolidated debt agreements.  This strategy may be used in controlling our overall cost of capital associated with such borrowings.

The following table summarizes our portfolio of forward starting swaps at June 30, 2018:

Hedged Transaction
Number and Type
of Derivatives
Outstanding
Notional
Amount
Expected Settlement
Date
Average Rate
Locked
Accounting
Treatment
Future long-term debt offering
2 forward starting swaps
$175.0
2/2019
2.56%
Cash flow hedge

As a result of market conditions in January 2018, we elected to terminate $100 million notional amount of the forward starting swaps that were outstanding at December 31, 2017, which resulted in cash proceeds totaling $1.5 million for the first quarter of 2018.

In January 2018, we sold swaptions related to our interest rate hedging activities that resulted in the recognition of $7.2 million of cash gains that were reflected as a reduction in interest expense for the first quarter of 2018.  Likewise, in April 2018, we sold swaptions related to our interest rate hedging activities that resulted in the recognition of $11.8 million of cash gains that were reflected as a reduction in interest expense for the second quarter of 2018.  The January 2018 swaptions expired in March 2018 and the April 2018 swaptions expired in June 2018.

Commodity Hedging Activities
The prices of natural gas, NGLs, crude oil, petrochemicals and refined products are subject to fluctuations in response to changes in supply and demand, market conditions and a variety of additional factors that are beyond our control.  In order to manage such price risks, we enter into commodity derivative instruments such as physical forward contracts, futures contracts, fixed-for-float swaps and basis swaps.  

At June 30, 2018, our predominant commodity hedging strategies consisted of (i) hedging anticipated future purchases and sales of commodity products associated with transportation, storage and blending activities, (ii) hedging natural gas processing margins and (iii) hedging the fair value of commodity products held in inventory.  
The objective of our anticipated future commodity purchases and sales hedging program is to hedge the margins of certain transportation, storage, blending and operational activities by locking in purchase and sale prices through the use of derivative instruments and related contracts.

The objective of our natural gas processing hedging program is to hedge an amount of earnings associated with these activities.  We achieve this objective by executing fixed-price sales for a portion of our expected equity NGL production using derivative instruments and related contracts.  For certain natural gas processing contracts, the hedging of expected equity NGL production also involves the purchase of natural gas for plant thermal reduction, which is hedged using derivative instruments and related contracts.

The objective of our inventory hedging program is to hedge the fair value of commodity products currently held in inventory by locking in the sales price of the inventory through the use of derivative instruments and related contracts.

The following table summarizes our portfolio of commodity derivative instruments outstanding at June 30, 2018 (volume measures as noted):
 
 
Volume (1)
Accounting
Derivative Purpose
Current (2)
Long-Term (2)
Treatment
Derivatives designated as hedging instruments:
   
Natural gas processing:
   
Forecasted natural gas purchases for plant thermal reduction (billion cubic feet (“Bcf”))
16.2
n/a
Cash flow hedge
Octane enhancement:
   
Forecasted purchase of NGLs (million barrels (“MMBbls”))
0.9
n/a
Cash flow hedge
Forecasted sales of octane enhancement products (MMBbls)
0.9
n/a
Cash flow hedge
Natural gas marketing:
   
Natural gas storage inventory management activities (Bcf)
1.8
n/a
Fair value hedge
NGL marketing:
   
Forecasted purchases of NGLs and related hydrocarbon products (MMBbls)
49.9
n/a
Cash flow hedge
Forecasted sales of NGLs and related hydrocarbon products (MMBbls)
64.1
n/a
Cash flow hedge
NGLs inventory management activities (MMBbls)
0.5
n/a
Fair value hedge
Refined products marketing:
 
  
Forecasted purchase of refined products (MMBbls)
0.9
n/a
Cash flow hedge
Forecasted sales of refined products (MMBbls)
1.2
n/a
Cash flow hedge
Refined products inventory management activities (MMBbls)
0.1
n/a
Fair value hedge
Crude oil marketing:
  
 
Forecasted purchases of crude oil (MMBbls)
9.1
4.1
Cash flow hedge
Forecasted sales of crude oil (MMBbls)
9.9
4.1
Cash flow hedge
Derivatives not designated as hedging instruments:
   
Natural gas risk management activities (Bcf) (3,4)
92.5
2.9
Mark-to-market
Refined products risk management activities (MMBbls) (4)
1.4
n/a
Mark-to-market
Crude oil risk management activities (MMBbls) (4)
68.5
29.0
Mark-to-market
 
(1)   Volume for derivatives designated as hedging instruments reflects the total amount of volumes hedged whereas volume for derivatives not designated as hedging instruments reflects the absolute value of derivative notional volumes.
(2)   The maximum term for derivatives designated as cash flow hedges, derivatives designated as fair value hedges and derivatives not designated as hedging instruments is December 2020, November 2018 and December 2020, respectively.
(3)   Current and long-term volumes include 45.8 Bcf and 0.8 Bcf, respectively, of physical derivative instruments that are predominantly priced at a market-based index plus a premium or minus a discount related to location differences.
(4)   Reflects the use of derivative instruments to manage risks associated with transportation, processing and storage assets.

The carrying amount of our inventories subject to fair value hedges was $42.8 million and $84.0 million at June 30, 2018 and December 31, 2017, respectively.  These amounts, which are presented in “Inventories” on our Unaudited Condensed Consolidated Balance Sheets, are inclusive of cumulative fair value hedging adjustments of $1.4 million and $7.0 million at June 30, 2018 and December 31, 2017, respectively.
 
Tabular Presentation of Fair Value Amounts, and Gains and Losses on
  Derivative Instruments and Related Hedged Items
The following table provides a balance sheet overview of our derivative assets and liabilities at the dates indicated:

  
 
Asset Derivatives
 
Liability Derivatives
 
  
 
June 30, 2018
 
December 31, 2017
 
June 30, 2018
 
December 31, 2017
 
  
 
Balance
Sheet
Location
 
Fair
Value
 
Balance
Sheet
Location
 
Fair
Value
 
Balance
Sheet
Location
 
Fair
Value
 
Balance
Sheet
Location
 
Fair
Value
 
Derivatives designated as hedging instruments
 
Interest rate derivatives
 
Current assets
 
$
13.0
 
Current assets
 
$
--
 
Current
liabilities
 
$
--
 
Current
liabilities
 
$
1.5
 
Interest rate derivatives
 
Other assets
  
--
 
Other assets
  
0.1
 
Other liabilities
  
--
 
Other liabilities
  
0.2
 
Total interest rate derivatives
    
13.0
    
0.1
    
--
    
1.7
 
Commodity derivatives
 
Current assets
  
142.7
 
Current assets
  
109.5
 
Current
liabilities
  
141.1
 
Current
liabilities
  
104.4
 
Commodity derivatives
 
Other assets
  
39.3
 
Other assets
  
6.4
 
Other liabilities
  
39.2
 
Other liabilities
  
6.8
 
Total commodity derivatives
 
 
  
182.0
 
 
  
115.9
 
 
  
180.3
 
 
  
111.2
 
Total derivatives designated as hedging instruments
   
$
195.0
   
$
116.0
   
$
180.3
   
$
112.9
 
   
 
    
 
    
 
    
 
    
Derivatives not designated as hedging instruments
 
Commodity derivatives
 
Current assets
 
$
9.4
 
Current assets
 
$
43.9
 
Current
liabilities
 
$
255.8
 
Current
liabilities
 
$
62.3
 
Commodity derivatives
 
Other assets
  
0.2
 
Other assets
  
1.9
 
Other liabilities
  
23.3
 
Other liabilities
  
3.4
 
Total commodity derivatives
 
 
 
$
9.6
 
 
 
$
45.8
 
 
 
$
279.1
 
 
 
$
65.7
 

Certain of our commodity derivative instruments are subject to master netting arrangements or similar agreements.  The following tables present our derivative instruments subject to such arrangements at the dates indicated:

 
Offsetting of Financial Assets and Derivative Assets
 
 
Gross
Amounts of
Recognized
Assets
 
Gross
Amounts
Offset in the
Balance Sheet
 
Amounts
of Assets
Presented
in the
Balance Sheet
 
Gross Amounts Not Offset
in the Balance Sheet
 
Amounts That
Would Have
Been Presented
On Net Basis
 
Financial
Instruments
  
Cash
Collateral
Received
  
Cash
Collateral
Paid
 
 
(i)
 
(ii)
 
(iii) = (i) – (ii)
 
(iv)
 
(v) = (iii) + (iv)
 
As of June 30, 2018:
                     
Interest rate derivatives
 
$
13.0
  
$
--
  
$
13.0
  
$
--
  
$
--
  
$
--
  
$
13.0
 
Commodity derivatives
  
191.6
   
--
   
191.6
   
(185.6
)
  
--
   
--
   
6.0
 
As of December 31, 2017:
                            
Interest rate derivatives
 
$
0.1
  
$
--
  
$
0.1
  
$
(0.1
)
 
$
--
  
$
--
  
$
--
 
Commodity derivatives
  
161.7
   
--
   
161.7
   
(157.8
)
  
--
   
--
   
3.9
 

 
Offsetting of Financial Liabilities and Derivative Liabilities
 
 
Gross
Amounts of
Recognized
Liabilities
 
Gross
Amounts
Offset in the
Balance Sheet
 
Amounts
of Liabilities
Presented
in the
Balance Sheet
 
Gross Amounts Not Offset
in the Balance Sheet
 
Amounts That
Would Have
Been Presented
On Net Basis
 
Financial
Instruments
  
Cash
Collateral
Received
  
Cash
Collateral
Paid
 
 
(i)
 
(ii)
 
(iii) = (i) – (ii)
 
(iv)
 
(v) = (iii) + (iv)
 
As of June 30, 2018:
                     
Commodity derivatives
 
$
459.4
  
$
--
  
$
459.4
  
$
(185.6
)
 
$
--
  
$
(272.9
)
 
$
0.9
 
As of December 31, 2017:
                            
Interest rate derivatives
 
$
1.7
  
$
--
  
$
1.7
  
$
(0.1
)
 
$
--
  
$
--
  
$
1.6
 
Commodity derivatives
  
176.9
   
--
   
176.9
   
(157.8
)
  
--
   
(17.3
)
  
1.8
 

Derivative assets and liabilities recorded on our Unaudited Condensed Consolidated Balance Sheets are presented on a gross-basis and determined at the individual transaction level.  The tabular presentation above provides a means for comparing the gross amount of derivative assets and liabilities, excluding associated accounts payable and receivable, to the net amount that would likely be receivable or payable under a default scenario based on the existence of rights of offset in the respective derivative agreements.  Any cash collateral paid or received is reflected in these tables, but only to the extent that it represents variation margins.  Any amounts associated with derivative prepayments or initial margins that are not influenced by the derivative asset or liability amounts or those that are determined solely on their volumetric notional amounts are excluded from these tables.

The following tables present the effect of our derivative instruments designated as fair value hedges on our Unaudited Condensed Statements of Consolidated Operations for the periods indicated:

Derivatives in Fair Value
Hedging Relationships
 
Location
 
Gain (Loss) Recognized in
Income on Derivative
 
 
  
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
 
2018
  
2017
  
2018
  
2017
 
Interest rate derivatives
Interest expense
 
$
0.6
  
$
0.4
  
$
1.3
  
$
(0.5
)
Commodity derivatives
Revenue
  
4.8
   
18.8
   
4.6
   
37.6
 
Total
 
 
$
5.4
  
$
19.2
  
$
5.9
  
$
37.1
 

Derivatives in Fair Value
Hedging Relationships
 
Location
 
Gain (Loss) Recognized in
Income on Hedged Item
 
 
  
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
 
2018
  
2017
  
2018
  
2017
 
Interest rate derivatives
Interest expense
 
$
(0.6
)
 
$
(0.3
)
 
$
(1.4
)
 
$
0.6
 
Commodity derivatives
Revenue
  
(4.9
)
  
(16.3
)
  
(1.8
)
  
(28.7
)
Total
 
 
$
(5.5
)
 
$
(16.6
)
 
$
(3.2
)
 
$
(28.1
)

The following tables present the effect of our derivative instruments designated as cash flow hedges on our Unaudited Condensed Statements of Consolidated Operations and Unaudited Condensed Statements of Consolidated Comprehensive Income for the periods indicated:

Derivatives in Cash Flow
Hedging Relationships
 
Change in Value Recognized in
Other Comprehensive Income (Loss) on Derivative
 
 
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
2018
  
2017
  
2018
  
2017
 
Interest rate derivatives
 
$
3.5
  
$
(6.9
)
 
$
14.6
  
$
(4.5
)
Commodity derivatives – Revenue (1)
  
(14.2
)
  
31.4
   
(11.2
)
  
179.0
 
Commodity derivatives – Operating costs and expenses (1)
  
0.6
   
(1.0
)
  
1.0
   
(3.8
)
Total
 
$
(10.1
)
 
$
23.5
  
$
4.4
  
$
170.7
 
  
(1)   The fair value of these derivative instruments will be reclassified to their respective locations on the Unaudited Condensed Statement of Consolidated Operations upon settlement of the underlying derivative transactions, as appropriate.
 


Derivatives in Cash Flow
Hedging Relationships
Location
 
Gain (Loss) Reclassified from
Accumulated Other Comprehensive Income (Loss) to Income
 
 
  
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
 
2018
  
2017
  
2018
  
2017
 
Interest rate derivatives
Interest expense
 
$
(9.4
)
 
$
(10.0
)
 
$
(19.9
)
 
$
(19.6
)
Commodity derivatives
Revenue
  
(39.4
)
  
46.0
   
(25.4
)
  
38.5
 
Commodity derivatives
Operating costs and expenses
  
0.2
   
--
   
0.7
   
0.4
 
Total
 
 
$
(48.6
)
 
$
36.0
  
$
(44.6
)
 
$
19.3
 

Over the next twelve months, we expect to reclassify $37.0 million of losses attributable to interest rate derivative instruments from accumulated other comprehensive loss to earnings as an increase in interest expense.  Likewise, we expect to reclassify $4.3 million of net gains attributable to commodity derivative instruments from accumulated other comprehensive income to earnings, $4.4 million as an increase in revenue and $0.1 million as an increase in operating costs and expenses.

The following table presents the effect of our derivative instruments not designated as hedging instruments on our Unaudited Condensed Statements of Consolidated Operations for the periods indicated:

Derivatives Not Designated
as Hedging Instruments
Location
 
Gain (Loss) Recognized in
Income on Derivative
 
 
  
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
 
2018
  
2017
  
2018
  
2017
 
Commodity derivatives
Revenue
 
$
(406.3
)
 
$
18.7
  
$
(559.8
)
 
$
34.4
 
Commodity derivatives
Operating costs and expenses
  
--
   
(0.8
)
  
(1.5
)
  
3.7
 
Total
 
 
$
(406.3
)
 
$
17.9
  
$
(561.3
)
 
$
38.1
 

The $561.3 million loss recognized during the 2018 earnings from derivatives not designated as hedging instruments reflects $106.9 million of realized losses on such instruments.  It does not reflect the $8.1 million of unrealized losses from fair value hedges.  In the aggregate, our unrealized mark-to-market losses for the six months ended June 30, 2018 were $462.5 million inclusive of all derivative instrument types.   The following table summarizes the impact of net unrealized, mark-to-market losses on our gross operating margin by segment for the six months ended June 30, 2018:

Unrealized mark-to-market gains (losses) by segment:
   
NGL Pipelines & Services
 
$
7.8
 
Crude Oil Pipelines & Services
  
(467.5
)
Natural Gas Pipelines & Services
  
(2.5
)
Petrochemical & Refined Products Services
  
(0.3
)
Total
 
$
(462.5
)

Fair Value Measurements
The following tables set forth, by level within the Level 1, 2 and 3 fair value hierarchy, the carrying values of our financial assets and liabilities at the dates indicated.  These assets and liabilities are measured on a recurring basis and are classified based on the lowest level of input used to estimate their fair value.  Our assessment of the relative significance of such inputs requires judgment.

The values for commodity derivatives are presented before and after the application of Rule 814 of the Chicago Mercantile Exchange (“CME”), which deems that financial instruments cleared by the CME are settled daily in connection with variation margin payments.  As a result of this exchange rule, CME-related derivatives are considered to have no fair value at the balance sheet date for financial reporting purposes; however, the derivatives remain outstanding and subject to future commodity price fluctuations until they are settled in accordance with their contractual terms.  Derivative transactions cleared on exchanges other than the CME (e.g., the Intercontinental Exchange or ICE) continue to be reported on a gross basis.

 
 
June 30, 2018
Fair Value Measurements Using
    
 
 
Quoted Prices
in Active
Markets for
Identical Assets
and Liabilities
(Level 1)
  
Significant
Other
Observable
Inputs
(Level 2)
  
Significant
Unobservable
Inputs
(Level 3)
  
Total
 
Financial assets:
            
Interest rate derivatives
 
$
--
  
$
13.0
  
$
--
  
$
13.0
 
Commodity derivatives:
                
Value before application of CME Rule 814
  
92.9
   
224.0
   
4.8
   
321.7
 
Impact of CME Rule 814 change
  
(6.9
)
  
(123.2
)
  
--
   
(130.1
)
Total commodity derivatives
  
86.0
   
100.8
   
4.8
   
191.6
 
Total financial assets
 
$
86.0
  
$
113.8
  
$
4.8
  
$
204.6
 
 
                
Financial liabilities:
                
Liquidity Option Agreement
 
$
--
  
$
--
  
$
350.3
  
$
350.3
 
Interest rate derivatives
  
--
   
--
   
--
   
--
 
Commodity derivatives:
                
Value before application of CME Rule 814
  
119.5
   
729.1
   
3.5
   
852.1
 
Impact of CME Rule 814 change
  
(34.3
)
  
(358.4
)
  
--
   
(392.7
)
Total commodity derivatives
  
85.2
   
370.7
   
3.5
   
459.4
 
Total financial liabilities
 
$
85.2
  
$
370.7
  
$
353.8
  
$
809.7
 

 
 
December 31, 2017
Fair Value Measurements Using
    
 
 
Quoted Prices
in Active
Markets for
Identical Assets
and Liabilities
(Level 1)
  
Significant
Other
Observable
Inputs
(Level 2)
  
Significant
Unobservable
Inputs
(Level 3)
  
Total
 
Financial assets:
            
Interest rate derivatives
 
$
--
  
$
0.1
  
$
--
  
$
0.1
 
Commodity derivatives:
                
Value before application of CME Rule 814
  
47.1
   
184.9
   
2.9
   
234.9
 
Impact of CME Rule 814 change
  
(47.1
)
  
(26.1
)
  
--
   
(73.2
)
Total commodity derivatives
  
--
   
158.8
   
2.9
   
161.7
 
Total financial assets
 
$
--
  
$
158.9
  
$
2.9
  
$
161.8
 
 
                
Financial liabilities:
                
Liquidity Option Agreement
 
$
--
  
$
--
  
$
333.9
  
$
333.9
 
Interest rate derivatives
  
--
   
1.7
   
--
   
1.7
 
Commodity derivatives:
                
Value before application of CME Rule 814
  
118.4
   
270.6
   
1.7
   
390.7
 
Impact of CME Rule 814 change
  
(118.4
)
  
(95.4
)
  
--
   
(213.8
)
Total commodity derivatives
  
--
   
175.2
   
1.7
   
176.9
 
Total financial liabilities
 
$
--
  
$
176.9
  
$
335.6
  
$
512.5
 

Our Level 3 financial liabilities at June 30, 2018 and December 31, 2017 primarily reflect the fair value assigned to the Liquidity Option Agreement (see Note 16) at each measurement date.  The carrying value of the Liquidity Option Agreement (a long-term liability) was $350.3 million and $333.9 million at June 30, 2018 and December 31, 2017, respectively.

The following table sets forth a reconciliation of changes in the fair values of our recurring Level 3 financial assets and liabilities on a combined basis for the periods indicated:

 
  
 
For the Six Months
Ended June 30,
 
 
Location 
 
2018
  
2017
 
Financial liability balance, net, January 1
 
 
$
(332.7
)
 
$
(268.2
)
Total gains (losses) included in:
 
        
Net income (1)
Revenue
  
(0.5
)
  
0.7
 
Net income
Other expense, net
  
(7.5
)
  
(5.5
)
Other comprehensive income (loss)
Commodity derivative instruments – changes in fair value of cash flow hedges
  
--
   
--
 
Settlements (1)
Revenue
  
(1.2
)
  
(1.4
)
Transfers out of Level 3
   
--
   
--
 
Financial liability balance, net, March 31
 
  
(341.9
)
  
(274.4
)
Total gains (losses) included in:
 
        
Net income (1)
Revenue
  
1.3
   
0.1
 
Net income
Other expense, net
  
(8.9
)
  
(18.6
)
Other comprehensive income (loss)
 
Commodity derivative instruments – changes in fair value of cash flow hedges
  
--
   
0.1
 
Settlements (1)
Revenue
  
0.5
   
(0.7
)
Transfers out of Level 3
   
--
   
--
 
Financial liability balance, net, June 30
 
 
$
(349.0
)
 
$
(293.5
)
  
(1)   There were unrealized gains of $1.8 million and $0.1 million included in these amounts for the three and six months ended June 30, 2018, respectively. There were unrealized losses of $0.6 million and $1.3 million included in these amounts for the three and six months ended June 30, 2017, respectively.
 

The following table provides quantitative information regarding our recurring Level 3 fair value measurements for commodity derivatives at June 30, 2018:

 
 
Fair Value
 
 
 
   
 
 
Financial
Assets
  
Financial
Liabilities
 
Valuation
Techniques
Unobservable
Input
Range
Commodity derivatives – Crude oil
 
$
4.8
  
$
3.5
 
Discounted cash flow
Forward commodity prices
$65.01-$76.84/barrel
   Total
 
$
4.8
  
$
3.5
      

With respect to commodity derivatives, we believe forward commodity prices are the most significant unobservable inputs in determining our Level 3 recurring fair value measurements at June 30, 2018.  In general, changes in the price of the underlying commodity increases or decreases the fair value of a commodity derivative depending on whether the derivative was purchased or sold.  We generally expect changes in the fair value of our derivative instruments to be offset by corresponding changes in the fair value of our hedged exposures.

Nonrecurring Fair Value Measurements
The following table summarizes our non-cash asset impairment charges for long-lived assets by segment during each of the periods indicated:

 
 
For the Three Months
Ended June 30,
  
For the Six Months
Ended June 30,
 
 
 
2018
  
2017
  
2018
  
2017
 
NGL Pipelines & Services
 
$
12.4
  
$
2.8
  
$
12.4
  
$
3.0
 
Crude Oil Pipelines & Services
  
0.1
   
0.6
   
0.3
   
0.6
 
Natural Gas Pipelines & Services
  
1.8
   
9.7
   
2.5
   
9.9
 
Petrochemical & Refined Products Services
  
1.5
   
--
   
1.5
   
--
 
Total
 
$
15.8
  
$
13.1
  
$
16.7
  
$
13.5
 

Impairment charges are primarily a component of “Operating costs and expenses” on our Unaudited Condensed Statements of Consolidated Operations.

Total asset impairment and related charges during the six months ended June 30, 2018 and June 30, 2017 include impairment charges attributable to the write-down of spare parts classified as current assets of $0.1 million and $11.7 million, respectively.

Other Fair Value Information
The carrying amounts of cash and cash equivalents (including restricted cash balances), accounts receivable, commercial paper notes and accounts payable approximate their fair values based on their short-term nature.  The estimated total fair value of our fixed-rate debt obligations was $23.61  billion and $23.47 billion at June 30, 2018 and December 31, 2017, respectively.  The aggregate carrying value of these debt obligations was $23.15 billion and $21.48 billion at June 30, 2018 and December 31, 2017, respectively.  These values are based on quoted market prices for such debt or debt of similar terms and maturities (Level 2), our credit standing and the credit standing of our counterparties.  Changes in market rates of interest affect the fair value of our fixed-rate debt.  The carrying values of our variable-rate long-term debt obligations approximate their fair values since the associated interest rates are market-based.  We do not have any long-term investments in debt or equity securities recorded at fair value.