Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2012

Aggregate Fair Value, Amortized Cost, Gross Unrealized Gains and Gross Unrealized Losses on Available-for-Sale Marketable Securities

The aggregate fair value, amortized cost, gross unrealized gains and gross unrealized losses on available-for-sale marketable securities are as follows (in thousands):

	December 31, 2011
	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses
Washington DC tax exempt bonds	$	10,516	$	10,226	$	290	$	—