(4) Investments

Investments at December 31, 2011 were comprised of the following (in thousands):

	Amortized Cost		Fair Value(1)
Marketable debt securities – current (U.S. Treasury securities, due in less than one year)	$	20,004	$	20,020
Marketable debt securities – non-current (U.S. Treasury securities, due between one and two years)		10,017		10,042
	$	30,021	$	30,062

(1) See Notes 1 and 2 for discussion of fair value measurements.

During 2011, $10.0 million of marketable debt securities matured and were redeemed at face value. We held no short-term or long-term investments at January 1, 2011.