The carrying amounts of our cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the short maturity of these instruments and are classified as Level 1 in the fair value hierarchy. The carrying value of bank debt approximates fair value, as the interest rate on the bank debt is variable and approximates current market rates. As a result, the fair value measurement of our bank debt is classified as Level 2 in the fair value hierarchy.

Concentrations of Credit Risk - Financial instruments that may subject us to concentration of credit risk consist primarily of cash and cash equivalents and accounts receivable. We place our cash and cash equivalents with highly-rated financial institutions, limiting the amount of credit exposure with any one financial institution. Our client base consists of large numbers of geographically diverse customers dispersed throughout the United States; thus, concentration of credit risk with respect to accounts receivable is not significant.

Bonds - We held corporate and municipal bonds with net par values totaling $58.9 million and $55.7 million at December 31, 2019 and 2018, respectively. All bonds are investment grade and are classified as available-for-sale. Our bonds have maturity dates or callable dates ranging from January 2020 through February 2024, and are included in “Funds held for clients — current” in the accompanying Consolidated Balance Sheets based on our intent and ability to sell these investments at any time under favorable conditions.

The following table summarizes our bond activity for the years ended December 31, 2019 and 2018 (in thousands):

	2019			2018
Fair value at January 1	$	56,556		$	51,101
Purchases		27,216			18,426
Sales		(1,686	)		(1,793	)
Maturities and calls		(22,272	)		(10,445	)
Decrease in bond premium		(460	)		(377	)
Fair market value adjustment		1,305			(356	)
Fair value at December 31	$	60,659		$	56,556

In addition to the available-for-sale securities discussed above, we also hold certified deposits and other depository assets in the amount of $2.5 million and $2.3 million at December 31, 2019 and December 31, 2018, respectively, related to the funds held for clients.

Interest Rate Swaps - We do not purchase or hold any derivative instruments for trading or speculative purposes. We utilize interest rate swaps to manage interest rate risk exposure associated with our floating-rate debt under the 2018 credit facility. Under these interest rate swap contracts, we receive cash flows from counterparties at variable rates based on LIBOR and pay the counterparties a fixed rate. To mitigate counterparty credit risk, we only enter into contracts with selected major financial institutions with investment grade ratings and continually assess their creditworthiness. There are no credit risk-related contingent features in our interest rate swaps nor do the swaps contain provisions under which we would be required to post collateral.

The designation of a derivative instrument as a hedge and its ability to meet the hedge accounting criteria determine how we reflect the change in fair value of the derivative instrument. A derivative qualifies for hedge accounting treatment if, at inception, it meets defined correlation and effectiveness criteria. These criteria require that the anticipated cash flows and/or changes in fair value of the hedging instrument substantially offset those of the position being hedged.

We had no fair value hedging instruments at December 31, 2019 or 2018. Our interest rate swaps are designated as cash flow hedges. Accordingly, the interest rate swaps are recorded as either an asset or liability in the accompanying Consolidated Balance Sheets at fair value. The mark-to-market gains or losses on the swaps are deferred and included as a component of accumulated other comprehensive loss (“AOCL”), net of tax, to the extent the hedge is determined to be effective, and reclassified to interest expense in the same period during which the hedged transaction affects earnings. The interest rate swaps are assessed for effectiveness and continued qualification for hedge accounting on a quarterly basis. For the years ended December 31, 2019 and 2018, the interest rate swaps were deemed to be highly effective.

The following table summarizes our outstanding interest rate swaps and their classification in the accompanying Consolidated Balance Sheets at December 31, 2019 and 2018 (in thousands). Refer to Note 7, Fair Value Measurements, to the accompanying consolidated financial statements for additional disclosures regarding fair value measurements.

	December 31, 2019
	Notional Amount		Fair Value			Balance Sheet Location
Interest rate swaps	$	45,000	$	(591	)	Other non-current liabilities
Interest rate swap	$	25,000	$	66		Other current assets

	December 31, 2018
	Notional Amount		Fair Value			Balance Sheet Location
Interest rate swaps	$	70,000	$	1,096		Other non-current assets

Under the terms of the interest rate swaps, we pay interest at a fixed rate of interest plus applicable margin as stated in the agreement, and receive interest that varies with the one-month LIBOR. The notional value, fixed rate of interest and expiration date of each interest rate swap as of December 31, 2019 is (i) $25 million – 1.300% - October 2020, (ii) $10 million – 1.120% - February 2021 and (iii) $20 million – 1.770% - May 2022 and (iv) $15 million – 2.640% - June 2023.

During the next twelve months, the amount of the December 31, 2019 AOCL balance that will be reclassified to earnings is expected to be immaterial. The following table summarizes the effects of the interest rate swap on our accompanying Consolidated Statements of Comprehensive Income for the years ended December 31, 2019 and 2018 (in thousands):

	(Loss) recognized in AOCL, net of tax						Gain reclassified from AOCL into expense
	Twelve Months Ended December 31,						Twelve Months Ended December 31,				Location
	2019			2018			2019		2018
Interest rate swaps	$	(1,222	)	$	(17	)	$	399	$	357	Interest expense