We have and may in the future use derivative financial instruments to hedge all or a portion of the interest rate risk associated with our borrowings. The principal objective of such arrangements is to minimize the risks and/or costs associated with our operating and financial structure as well as to hedge specific anticipated transactions. While these instruments may impact our periodic cash flows, they benefit us by minimizing the risks and/or costs previously described. The counterparties to these contractual arrangements are major financial institutions with which we and our affiliates may also have other financial relationships. In the event of nonperformance by the counterparties, we are potentially exposed to credit loss. However, because of the high credit ratings of the counterparties, we do not anticipate that any of the counterparties will fail to meet their obligations.

The following table summarizes the aggregate notional amount and estimated net fair value of our derivative instruments as of June 30, 2019 and December 31, 2018:

	As of June 30, 2019						As of December 31, 2018
	Notional		Fair Value of Assets		Fair Value of Liabilities		Notional		Fair Value of Assets		Fair Value of Liabilities
Cash flow hedges:
Interest rate swap	$	150,000	$	1,558	$	—	$	150,000	$	4,751	$	—
Interest rate collars		250,000		—		4,422		250,000		3,556		—
Forward interest rate swap		—		—		2,972		—		—		—
Total	$	400,000	$	1,558	$	7,394	$	400,000	$	8,307	$	—

On May 9, 2019, we entered into a forward-starting interest rate swap contract with a notional value of $150,000 and a strike of 2.176%. The forward interest rate swap has an effective date of June 17, 2021 and a maturity date of June 17, 2026. We designated this forward interest rate swap as a cash flow hedge at inception and determined that the hedge is highly effective in offsetting interest rate fluctuations associated with the identified indebtedness.

Effective interest rate swaps and caps are reported in accumulated other comprehensive income, and the fair value of these hedge agreements is included in other assets or other liabilities.

For our interest rate swap and collars that are considered highly effective hedges, we reclassified realized gains of $467 and $1,026 to earnings within interest expense for the three and six months ended June 30, 2019, respectively, and we expect $86 to be reclassified out of accumulated other comprehensive income to earnings over the next 12 months.