We use derivatives as part of our risk management program to manage the risks associated with the price volatility of interest rates, purchased power, generation, and natural gas costs for the benefit of our customers and shareholders. Our approach is non-speculative and designed to mitigate risk. Regulated hedging programs are approved by our state regulators.

We record derivative instruments on our balance sheets as an asset or liability measured at fair value unless they qualify for the normal purchases and sales exception and are so designated. We continually assess our contracts designated as normal and will discontinue the treatment of these contracts as normal if the required criteria are no longer met. Changes in the derivative's fair value are recognized currently in earnings unless specific hedge accounting criteria are met or we receive regulatory treatment for the derivative. For most energy-related physical and financial contracts in our regulated operations that qualify as derivatives, our regulators allow the effects of fair value accounting to be offset to regulatory assets and liabilities.

None of our derivatives are designated as hedging instruments, with the exception of our interest rate swaps, which have been designated as cash flow hedges. The following table shows our derivative assets and derivative liabilities:



	September 30, 2019				December 31, 2018
(in millions)	Derivative Assets		Derivative Liabilities		Derivative Assets		Derivative Liabilities
Other current
Natural gas contracts	$	8.9	$	22.3	$	7.7	$	5.3
FTRs	6.2		—		7.4		—
Coal contracts	0.3		0.1		0.2		0.1
Interest rate swaps	—		2.5		—		0.4
Total other current *	15.4		24.9		15.3		5.8

Other long-term
Natural gas contracts	—		2.2		0.4		0.2
Coal contracts	0.3		0.1		0.2		—
Interest rate swaps	—		4.4		—		1.9
Total other long-term *	0.3		6.7		0.6		2.1
Total	$	15.7	$	31.6	$	15.9	$	7.9

Realized gains (losses) on derivatives not designated as hedging instruments are primarily recorded in cost of sales on the income statements. Our estimated notional sales volumes and realized gains (losses) were as follows:



	Three Months Ended September 30, 2019				Three Months Ended September 30, 2018
(in millions)	Volumes	Gains (Losses)			Volumes	Gains
Natural gas contracts	37.8 Dth	$	(13.2	)	36.7 Dth	$	0.4
Petroleum products contracts	— gallons	—			1.3 gallons	0.5
FTRs	7.8 MWh	7.6			7.9 MWh	7.1
Total		$	(5.6	)		$	8.0



	Nine Months Ended September 30, 2019				Nine Months Ended September 30, 2018
(in millions)	Volumes	Gains (Losses)			Volumes	Gains (Losses)
Natural gas contracts	137.7 Dth	$	(16.8	)	124.7 Dth	$	(7.1	)
Petroleum products contracts	— gallons	—			5.1 gallons	1.3
FTRs	23.9 MWh	12.9			22.9 MWh	14.7
Total		$	(3.9	)		$	8.9

On our balance sheets, the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral are not offset against the fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement. At September 30, 2019 and December 31, 2018, we had posted cash collateral of $28.3 million and $2.7 million, respectively, in our margin accounts. These amounts were recorded on our balance sheets in other current assets. At December 31, 2018, we had also received cash collateral of $0.2 million in our margin accounts. This amount was recorded on our balance sheet in other current liabilities. We had not received any cash collateral at September 30, 2019.

The following table shows derivative assets and derivative liabilities if derivative instruments by counterparty were presented net on our balance sheets:



	September 30, 2019							December 31, 2018
(in millions)	Derivative Assets			Derivative Liabilities				Derivative Assets				Derivative Liabilities
Gross amount recognized on the balance sheet	$	15.7		$	31.6			$	15.9			$	7.9
Gross amount not offset on the balance sheet	(5.7		)	(23.9		)	⁽¹⁾	(4.0		)	⁽²⁾	(4.9		)	⁽³⁾
Net amount	$	10.0		$	7.7			$	11.9			$	3.0

Effective January 1, 2019, we adopted ASU 2017-12, Targeted Improvements to Accounting for Hedging Activities. The amendments in this update expand the strategies that qualify for hedge accounting, amend the presentation and disclosure requirements related to hedging activities, and provide overall targeted improvements to simplify hedge accounting in certain situations. The adoption of this standard did not have a significant impact on our financial statements.

As of September 30, 2019, we had two interest rate swaps with a combined notional value of $250.0 million to hedge the variable interest rate risk associated with our 2007 Junior Notes. The swaps provide a fixed interest rate of 4.9765% on $250.0 million of the $500.0 million of outstanding 2007 Junior Notes through November 15, 2021. As these swaps qualified for cash flow hedge accounting treatment, the related gains and losses are being deferred in accumulated other comprehensive loss and are being amortized to interest expense as interest is accrued on the 2007 Junior Notes.

We previously entered into forward interest rate swap agreements to mitigate the interest rate exposure associated with the issuance of long-term debt related to the acquisition of Integrys. These swap agreements were settled in 2015, and we continue to amortize amounts out of accumulated other comprehensive loss into interest expense over the periods in which the interest costs are recognized in earnings.

The table below shows the amounts related to these cash flow hedges recorded in other comprehensive loss and in earnings, along with our total interest expense on the income statements:



	Three Months Ended September 30					Nine Months Ended September 30
(in millions)	2019			2018		2019			2018
Derivative (losses) gains recognized in other comprehensive loss	$	(0.5	)	$	0.4	$	(5.3	)	$	0.4
Net derivative gains reclassified from accumulated other comprehensive loss to interest expense	0.2			0.2		1.0			1.3
Total interest expense line item on the income statements	125.8			112.0		374.3			327.2

We estimate that during the next twelve months $0.5 million will be reclassified from accumulated other comprehensive loss as an increase to interest expense.