Investments

Certificates of Deposit – We held approximately $2.2 million and $2.9 million in certificates of deposit at September 30, 2018 and December 31, 2017, respectively. At September 30, 2018, the certificates of deposit bear interest ranging from 1.70% to 1.95% per annum and have various maturities ranging from less than one month to approximately 2 months.

Investments Held to Maturity – Our investments held to maturity are comprised of $1.3 million of corporate notes and bonds with original maturities ranging from less than one month to approximately 2 months. The investments have moderate risk with S&P ratings ranging from AAA to BBB-.

We record the amortized cost basis and accrued interest of the corporate notes and bonds in the Consolidated Balance Sheets. We record the interest and amortization of bond premium to interest income in the Consolidated Statements of Income.

The following summarizes the amortized cost and estimated fair value of our investments held to maturity as of September 30, 2018 and December 31, 2017:



	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Loss)			Fair Value (Level 1)
September 30, 2018:	(in thousands)
Current assets:
Investments held to maturity	$	1,252	$	—	$	(1	)	$	1,251
Non current assets:
Investments held to maturity	—		—		—			—
Total	$	1,252	$	—	$	(1	)	$	1,251

December 31, 2017:
Current assets:
Investments held to maturity	$	6,077	$	—	$	(6	)	$	6,071
Non current assets:
Investments held to maturity	—		—		—			—
Total	$	6,077	$	—	$	(6	)	$	6,071