Cash, Cash Equivalents and Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2013

Cash, Cash Equivalents and Marketable Securities [Abstract]

Summary of investments in cash, cash equivalents and marketable securities

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

	March 31,			December 31,
	2013			2012
	(in thousands)
Overnight Holdings
Money market funds (cash equivalents)	$	178,040		$	255,000
Investment Holdings
Money market funds (cash equivalents)		38,722			26,087
Marketable securities		51,397			16,904
		268,159			297,991
Cash held in demand accounts		22,345			21,732
Outstanding checks		(11,675	)		(38,275	)
Total cash, cash equivalents and marketable securities	$	278,829		$	281,448
Cash and cash equivalents	$	227,432		$	264,544
Marketable securities		51,397			16,904
	$	278,829		$	281,448

Summary of fair value measurements of financial assets

The following table summarizes the levels of fair value measurements of our financial assets:

	Fair Value Measurements
	(in thousands)
	March 31,
	2013		Level 1		Level 2		Level 3
Money market funds	$	216,762	$	216,762	$	—	$	—
Municipal bonds		51,397		—		51,397		—
Total	$	268,159	$	216,762	$	51,397	$	—

	Fair Value Measurements
	(in thousands)
	December 31,
	2012		Level 1		Level 2		Level 3
Money market funds	$	281,087	$	281,087	$	—	$	—
Municipal bonds		16,904		—		16,904		—
Total	$	297,991	$	281,087	$	16,904	$	—

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)
March 31, 2013:
Municipal bonds	$	51,342	$	56	$	(1	)	$	51,397
December 31, 2012:
Municipal bonds	$	16,878	$	29	$	(3	)	$	16,904

Contractual maturities of marketable securities

As of March 31, 2013, the contractual maturities of our marketable securities were as follows:

	Amortized Cost		Estimated Fair Value
	(in thousands)
Less than one year	$	23,231	$	23,255
One to five years		28,111		28,142
Total	$	51,342	$	51,397