Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2016

Available-for-sale Securities [Abstract]

Cash equivalents and marketable securities classified as available-for-sale

Total cash, cash equivalents and marketable securities are summarized as follows:



	As of December 31, 2016
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	10,681	$	10,681	$	—	$	—		0.41	%
U.S. Government bonds and notes	48,292		48,291		1		—			0.39	%
Corporate notes, bonds, commercial paper and other	62,178		62,199		—		(21)			0.66	%
Total cash equivalents and marketable securities	121,151		121,171		1		(21)
Cash	51,031		51,031		—		—
Total cash, cash equivalents and marketable securities	$	172,182	$	172,202	$	1	$	(21	)



	As of December 31, 2015
(Dollars in thousands)	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Weighted Rate of Return
Money market funds	$	77,804	$	77,804	$	—	$	—		0.12	%
U.S. Government bonds and notes	14,110		14,142		—		(32		)	0.48	%
Corporate notes, bonds, commercial paper and other	160,823		160,979		—		(156		)	0.45	%
Total cash equivalents and marketable securities	252,737		252,925		—		(188		)
Cash	34,969		34,969		—		—
Total cash, cash equivalents and marketable securities	$	287,706	$	287,894	$	—	$	(188	)

Available-for-sale securities reported at fair value

Available-for-sale securities are reported at fair value on the balance sheets and classified as follows:



	As of
	December 31, 2016		December 31, 2015
	(Dollars in thousands)
Cash equivalents	$	84,263	$	108,795
Short term marketable securities	36,888		143,942
Total cash equivalents and marketable securities	121,151		252,737
Cash	51,031		34,969
Total cash, cash equivalents and marketable securities	$	172,182	$	287,706

Estimated fair value of cash equivalents and marketable securities classified by date of contractual maturity and the length of time that the securities have been in a continuous unrealized loss position

The estimated fair value of cash equivalents and marketable securities classified by the length of time that the securities have been in a continuous unrealized loss position at December 31, 2016 and 2015 are as follows:



	Fair Value				Gross Unrealized Loss
	December 31, 2016		December 31, 2015		December 31, 2016			December 31, 2015
	(In thousands)
Less than one year
U.S. Government bonds and notes	$	18,395	$	14,110	$	—		$	(32	)
Corporate notes, bonds and commercial paper	54,377		145,563		(21		)	(156		)
Total Corporate notes, bonds, and commercial paper and U.S. Government bonds and notes	$	72,772	$	159,673	$	(21	)	$	(188	)