Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value of Financial Instruments

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, in thousands of dollars:

	Fair Value Measurements at
	March 31, 2019
	(unaudited)
					Significant
	Total Fair		Quoted Prices		Other		Significant
	Value at		in Active Markets		Observable		Unobservable
	March 31,		for Identical Assests		Inputs		Inputs
	2019		(Level 1)		(Level 2)		(Level 3)
Assets:
Cash and cash equivalents	$	122,778	$	122,778	$	—	$	—
Marketable securities
Corporate debt securities		170,165		246		169,919		—
Long term marketable securities
Corporate debt securities		521,398		450		520,948		—
Government debt securities		1,153		—		1,153		—
Other non-current assets
Marketable securities - restricted (SERP)		375		1		374		—
Total assets at fair value	$	815,869	$	123,475	$	692,394	$	—

	Fair Value Measurements at
	December 31, 2018
					Significant
	Total Fair		Quoted Prices		Other		Significant
	Value at		in Active Markets		Observable		Unobservable
	December 31,		for Identical Assests		Inputs		Inputs
	2018		(Level 1)		(Level 2)		(Level 3)
Assets:
Cash and cash equivalents	$	192,248	$	192,248	$	—	$	—
Marketable securities
Corporate debt securities		163,770		245		163,525		—
Long term marketable securities
Corporate debt securities		415,650		445		415,205		—
Government debt securities		3,148		—		3,148		—
Other non-current assets
Marketable securities - restricted (SERP)		326		1		325		—
Total assets at fair value	$	775,142	$	192,939	$	582,203	$	—

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, in thousands of dollars:

	March 31, 2019				December 31, 2018
	(unaudited)
	Carrying Value		Fair Value		Carrying Value		Fair Value
2023 Notes	$	333,310	$	388,664	$	329,462	$	375,834

Schedule of unrestricted available-for-sale marketable securities

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

	March 31, 2019		December 31, 2018
	(unaudited)
Corporate and government debt securities
Amortized cost	$	690,853	$	586,726
Gross unrealized gains		2,905		55
Gross unrealized losses		(1,042)		(4,213)
Total fair value	$	692,716	$	582,568

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, in thousands of dollars:

	March 31,
	2019
	(unaudited)
Less than 1 year	$	170,165
1 year to 2 years		170,246
2 years to 3 years		181,872
3 years to 4 years		170,433
Greater than 4 years		—
Total	$	692,716