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 March 31, 2019 and December 31, 2018:

	As of March 31, 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	$	3,522	$	—	$	150,000	$	4,751	$	—
Interest rate collars		250,000		1,805		1,460		250,000		3,556		—
Total	$	400,000	$	5,327	$	1,460	$	400,000	$	8,307	$	—

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 $559 to earnings within interest expense for the three months ended March 31, 2019, and we expect $1,363 to be reclassified out of accumulated other comprehensive income to earnings over the next 12 months.