Investments (Tables)

3 Months Ended

Mar. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities

The amortized cost, gross unrealized gains, gross unrealized losses, and fair market value of available-for-sale investment securities by major security type and class of security at March 31, 2015, and December 31, 2014 are as follows:

		Investments
(In thousands)		Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair market value
2015
	Federal agency notes	$	168,485	$	97	$	—		$	168,582
	Commercial paper	110,130		2		(149		)	109,983
	Mutual funds	468		297		—			765
	Total	$	279,083	$	396	$	(149	)	$	279,330
2014
	Federal agency notes	$	143,132	$	40	$	(33	)	$	143,139
	Commercial paper	108,371		1		(257		)	108,115
	Mutual funds	344		279		—			623
	Total	$	251,847	$	320	$	(290	)	$	251,877

Schedule of Maturities of Available-for-sale Securities

The maturities of available-for-sale securities at March 31, 2015 are as follows:

(In thousands)	Amortized cost		Fair market value
Federal agency notes
Due in one year or less	$	117,412	$	117,465
Due after one year through two years	51,073		51,117
Total	$	168,485	$	168,582
Commercial paper
Due in one year or less	$	77,447	$	77,365
Due after one year through two years	32,683		32,618
Total	$	110,130	$	109,983