Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2011

Marketable Securities [Abstract]

Schedule of Marketable Securities

The carrying amounts of marketable securities were as follows (in thousands):

September 30, 2011	Held-to-Maturity		Trading		Total
U.S. Government and agency obligations	$	40,218	$	—	$	40,218
Commercial paper	29,978		—		29,978
Municipal bonds	4,036		—		4,036
Corporate bonds	3,157		—		3,157
Total short-term marketable securities	77,389		—		77,389
U.S. Government and agency obligations	45,268		—		45,268
Municipal bonds	8,952		—		8,952
Corporate bonds	5,289		—		5,289
Total long-term marketable securities	59,509		—		59,509
Total marketable securities	$	136,898	$	—	$	136,898

December 31, 2010
U.S. Government and agency obligations	$	40,047	$	—	$	40,047
Commercial paper	33,971		—		33,971
Municipal bonds	10,896		—		10,896
Corporate bonds	10,122		—		10,122
Equity securities - mutual funds	—		14,411		14,411
Total short-term marketable securities	95,036		14,411		109,447
U.S. Government and agency obligations	30,618		—		30,618
Municipal bonds	3,641		—		3,641
Total long-term marketable securities	34,259		—		34,259
Total marketable securities	$	129,295	$	14,411	$	143,706

September 30, 2010
U.S. Government and agency obligations	$	44,407	$	—	$	44,407
Commercial paper	19,971		—		19,971
Municipal bonds	11,204		—		11,204
Equity securities - mutual funds	—		5,380		5,380
Total short-term marketable securities	75,582		5,380		80,962
U.S. Government and agency obligations	45,844		—		45,844
Municipal bonds	3,658		—		3,658
Total long-term marketable securities	49,502		—		49,502
Total marketable securities	$	125,084	$	5,380	$	130,464

Held-to-maturity Securities

Scheduled maturities of held-to-maturity investments were as follows (in thousands):

September 30, 2011
Due within one year	$	77,389
Due in one to five years	59,509
Total	$	136,898