Cash, Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2011

Cash, Cash Equivalents and Marketable Securities [Abstract]

Summary of investments in cash, cash equivalents and marketable securities

The following table summarizes our investments in cash equivalents and marketable securities held by investment managers and overnight investments:

	December 31,
	2011			2010
	(in thousands)
Overnight holdings:
Money market funds (cash equivalents)	$	71,350		$	157,680
Investment holdings:
Money market funds (cash equivalents)		59,587			72,258
Marketable securities		56,987			43,367
		187,924			273,305
Cash held in demand accounts		113,968			31,295
Outstanding checks		(33,697	)		(26,404	)
Total cash, cash equivalents and marketable securities	$	268,195		$	278,196
Cash and cash equivalents	$	211,208		$	234,829
Marketable securities		56,987			43,367
	$	268,195		$	278,196

Summary of fair value measurements of financial assets

The following tables summarize the levels of fair value measurements of our financial assets:

	Fair Value Measurements
			(in thousands)
	December 31,
	2011		Level 1		Level 2		Level 3
Money market funds	$	130,937	$	130,937	$	-	$	-
Municipal bonds		56,987		-		56,987		-
Total	$	187,924	$	130,937	$	56,987	$	-

	Fair Value Measurements
			(in thousands)
	December 31,
	2010		Level 1		Level 2		Level 3
Money market funds	$	229,938	$	229,938	$	-	$	-
Municipal bonds		43,367		-		43,367		-
Total	$	273,305	$	229,938	$	43,367	$	-

Summary of available-for-sale securities

The following is a summary of our available-for-sale marketable securities:

			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
			(in thousands)
December 31, 2011:
Municipal bonds	$	56,945	$	90	$	(48	)	$	56,987
December 31, 2010:
Municipal bonds	$	43,330	$	63	$	(26	)	$	43,367

Contractual maturities of marketable securities

As of December 31, 2011, the contractual maturities of our marketable securities were as follows:

	Amortized Cost		Estimated Fair Value
	(in thousands)
Less than one year	$	33,722	$	33,701
One to five years		23,223		23,286
Total	$	56,945	$	56,987