Cash Equivalents and Investments (Tables)

9 Months Ended

Sep. 30, 2017

Cash and Cash Equivalents [Abstract]

Summary of cash and available-for-sale securities

							Reported as:
	Amortized Cost		Unrealized Gains		Estimated Fair Value		Cash and Cash Equivalents		Short-Term Investments
(In thousands)
September 30, 2017
Cash	$	495,380	$	—	$	495,380	$	495,380	$	—
Money market funds	14,705		—		14,705		14,705		—
Commercial paper	2,060		—		2,060		—		2,060
Corporate securities	3,352		997		4,349		—		4,349
Total	$	515,497	$	997	$	516,494	$	510,085	$	6,409
December 31, 2016
Cash	$	147,150	$	—	$	147,150	$	147,150	$	—
Money market funds	4		—		4		4		—
Commercial paper	19,987		—		19,987		—		19,987
Total	$	167,141	$	—	$	167,141	$	147,154	$	19,987