Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

Fair Value Assets Measured on Recurring Basis

The composition of our financial instruments among the three Levels of the fair value hierarchy are as follows (in thousands):

	September 30, 2013
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	285,851	$	—	$	—	$	285,851
U.S. government and government agency debt securities		—		367,807		—		367,807
Corporate debt securities (1)		—		752,098		—		752,098
Municipal securities (1)		—		17,311		—		17,311
Total	$	285,851	$	1,137,216	$	—	$	1,423,067
Liabilities:
Contingent consideration	$	—	$	—	$	10,790	$	10,790
	December 31, 2012
	Level 1		Level 2		Level 3		Total
Assets:
Money market funds (1)	$	226,993	$	—	$	—	$	226,993
U.S. government and government agency debt securities		—		464,815		—		464,815
Corporate debt securities (1)		—		818,167		—		818,167
Municipal securities (1)		—		5,234		—		5,234
Total	$	226,993	$	1,288,216	$	—	$	1,515,209
Liabilities:
Interest rate swap agreements	$	—	$	2,423	$	—	$	2,423

(1) Includes amounts classified as cash and cash equivalents.