FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2018

FAIR VALUE MEASUREMENTS

Schedule of fair value measurements along with the level within the fair value hierarchy in which the fair value measurements fall

			Fair Value Measurement at March 31, 2018 Using:
			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
	Fair Value at		Identical Assets		Inputs		Inputs
(In thousands)	March 31, 2018		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents
Cash and money market	$	101,103	$	101,103	$	—	$	—
Certificates of deposit		25,198		—		25,198		—
Commercial paper		11,998		—		11,998		—
U.S. government agency securities		8,398		—		8,398		—
Corporate bonds		1,998		—		1,998		—
Available-for-sale
Marketable securities
Corporate bonds		345,123		—		345,123		—
Asset backed securities		253,547		—		253,547		—
U.S. government agency securities		194,024		—		194,024		—
Commercial paper		51,994		—		51,994		—
Certificates of deposit		48,786		—		48,786		—
Total	$	1,042,169	$	101,103	$	941,066	$	—

The following table presents the Company’s fair value measurements as of December 31, 2017 along with the level within the fair value hierarchy in which the fair value measurements in their entirety fall.

			Fair Value Measurement at December 31, 2017 Using:
			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
	Fair Value at		Identical Assets		Inputs		Inputs
(In thousands)	December 31, 2017		(Level 1)		(Level 2)		(Level 3)
Cash and cash equivalents
Cash and money market	$	61,297	$	61,297	$	—	$	—
Commercial paper		10,995				10,995		—
Certificates of deposit		1,499				1,499		—
U.S. government agency securities		3,700				3,700		—
Available-for-sale
Marketable securities
Corporate bonds		181,305		—		181,305		—
Asset backed securities		94,515		—		94,515		—
U.S. government agency securities		54,812		—		54,812		—
Commercial paper		9,946		—		9,946		—
Certificates of deposit		6,646		—		6,646		—
Total	$	424,715	$	61,297	$	363,418	$	—

Schedule of gross unrealized losses and fair values of investments in an unrealized loss position

		March 31, 2018
		Less than 12 months			12 months or greater				Total
(In thousands)		Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
Marketable securities
Corporate bonds	$	328,935	$	(1,073)	$	—	$	—	$	328,935	$	(1,073)
Asset backed securities		252,105		(841)		1,442		(2)		253,547		(843)
U.S. government agency securities		169,071		(237)		24,953		(46)		194,024		(283)
Commercial paper		51,425		(21)		—		—		51,425		(21)
Certificates of deposit		41,551		(79)		—		—		41,551		(79)
Total	$	843,087	$	(2,251)	$	26,395	$	(48)	$	869,482	$	(2,299)

Schedule of contractual maturities of available-for-sale investments

		Due one year or less			Due after one year through four years
(In thousands)		Cost		Fair Value		Cost		Fair Value
Marketable securities
Corporate bonds	$	224,976	$	224,287	$	121,217	$	120,836
U.S. government agency securities		174,495		174,218		19,812		19,806
Commercial paper		52,015		51,994		—		—
Certificates of deposit		46,888		46,820		1,976		1,966
Asset backed securities		30,844		30,753		223,546		222,794
Total	$	529,218	$	528,072	$	366,551	$	365,402