Investments

Certificates of Deposit – We held $10.8 million and $12.0 million in certificates of deposit at March 31, 2016 and December 31, 2015, respectively. At March 31, 2016, the certificates of deposit bear interest ranging from 0.30% to 0.90% per annum and have various maturities ranging from less than one month to approximately 12 months.

Investments Held to Maturity – Our investments held to maturity are comprised of $15.2 million of corporate notes and bonds with original maturities ranging from less than one month to approximately 12 months. The investments have moderate risk with S&P ratings ranging from AA+ 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

March 31, 2016 and December 31, 2015:



	Amortized Cost		Gross Unrealized Gain		Gross Unrealized (Loss)			Fair Value
March 31, 2016:	(in thousands)
Current assets:
Investments held to maturity	$	15,195	$	5	$	—		$	15,200
Non current assets:
Investments held to maturity	—		—		—			—
Total	$	15,195	$	5	$	—		$	15,200

December 31, 2015:
Current assets:
Investments held to maturity	$	12,444	$	—	$	(16	)	$	12,428
Non current assets:
Investments held to maturity	5,039		—		(17		)	5,022
Total	$	17,483	$	—	$	(33	)	$	17,450