Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Fair Value Measurements [Abstract]

Measurement of financial assets and liabilities at fair value on recurring basis

	June 30, 2012						December 31, 2011
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Financial assets
Cash and cash equivalents	$	178,718	$	—	$	—	$	133,429	$	—	$	—
Debt securities issued by the District of Columbia		9,105		—		—		10,516		—		—
Investments held through variable insurance products in a Rabbi Trust		—		14,500		—		—		13,985		—
Forward currency exchange contracts		—		69		—		—		34		—
Financial liabilities
Forward currency exchange contracts	$	—	$	82	$	—	$	—	$	334	$	—

Aggregate fair value, amortized cost, gross unrealized gains and gross unrealized losses on available-for-sale marketable securities

	June 30, 2012
	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses
Washington D.C. tax exempt bonds	$	9,105	$	8,970	$	135	$	—
	December 31, 2011
	Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses
Washington D.C. tax exempt bonds	$	10,516	$	10,226	$	290	$	—

Maturities of marketable securities

	June 30, 2012
	Fair Value		Amortized Cost
Less than one year	$	6,165	$	6,040
Matures in 1 to 5 years		2,940		2,930
Marketable securities	$	9,105	$	8,970