Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of fair value of the financial assets and liabilities

The Company’s financial assets that are required to be measured at fair value on a recurring basis are as follows (dollars in thousands):

			Fair Value Measurements at March 31, 2020 (unaudited)
	Total Fair Value at March 31, 2020		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents
Cash	$	19,911	$	19,911	$	—
Money market funds	205,856		205,856
Marketable securities
Corporate debt securities	174,939		—		174,939
Municipal debt securities	165		—		165
Long term marketable securities
Corporate debt securities	524,683		255		524,428
U.S. government agency debt securities	10,029		—		10,029
Other noncurrent assets
Marketable securities - restricted (SERP)	342		8		334
Total assets at fair value	$	935,925	$	226,030	$	709,895

			Fair Value Measurements at December 31, 2019 (unaudited)
	Total Fair Value at December 31, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents
Cash	$	78,912	$	78,912	$	—
Money market funds	102,469		102,469		—
Marketable securities
Corporate debt securities	165,527		—		165,527
Municipal debt securities	165		—		165
Long term marketable securities
Corporate debt securities	571,828		254		571,574
U.S. government agency and municipal debt securities	19,945		—		19,945
Other noncurrent assets
Marketable securities - restricted (SERP)	418		3		415
Total assets at fair value	$	939,264	$	181,638	$	757,626

Schedule of unrestricted available-for-sale marketable securities

Unrestricted available-for-sale marketable securities held by the Company are as follows, (dollars in thousands):

	March 31, 2020		December 31, 2019
	(unaudited)
Corporate and U.S. government agency and municipal debt securities
Amortized cost	$	710,072	$	747,598
Gross unrealized gains	5,362		10,031
Gross unrealized losses	(5,618)		(164)
Total fair value	$	709,816	$	757,465

Schedule of contractual maturities of the unrestricted available-for-sale marketable securities held

The contractual maturities of the unrestricted available-for-sale marketable securities held by the Company are as follows, (dollars in thousands):

	March 31, 2020
	(unaudited)
Less than 1 year	$	175,104
1 year to 2 years	181,141
2 years to 3 years	199,207
3 years to 4 years	154,364
Greater than 4 years	—
Total	$	709,816

Schedule of financial liabilities that are not carried at fair value

The following table sets forth the Company’s financial liabilities that are not carried at fair value, (dollars in thousands):

	March 31, 2020				December 31, 2019
	(unaudited)
	Carrying Value		Fair Value (Level 2)		Carrying Value		Fair Value (Level 2)
2023 Notes	$	349,232	$	328,038	$	345,170	$	366,023