Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2012

Summary of Significant Accounting Policies [Abstract]

Fair Value Measurements

The following table represents the fair value hierarchy based upon three levels of inputs, of which Levels 1 and 2 are considered observable and Level 3 is unobservable, for our financial assets and liabilities measured at fair value (in thousands):

	December 31, 2012						December 31, 2011
	Level 1		Level 2		Total		Level 1		Level 2		Total
Assets:
Cash and cash equivalents:
Money market funds	$	23,119	$	—	$	23,119	$	77,174	$	—	$	77,174
Commercial paper		—		38,582		38,582		—		4,798		4,798
Short-term investments:
Commercial paper		—		32,100		32,100		—		12,097		12,097
U.S. government agency bonds		—		748		748		—		—		—
Total	$	23,119	$	71,430	$	94,549	$	77,174	$	16,895	$	94,069
Liabilities:
Interest rate swap contracts (1)	$	—	$	1,069	$	1,069	$	—	$	1,005	$	1,005
Total	$	—	$	1,069	$	1,069	$	—	$	1,005	$	1,005

(1) As of December 31, 2012 and 2011, the fair value of the interest rate swap contracts were classified on our Balance Sheet in other non-current liabilities.

Carrying value and estimated fair value of debt

The following table indicates the carrying value and estimated fair value of our debt as of the indicated periods (in millions):

	December 31, 2012				December 31, 2011
	Carrying Value		Fair Value		Carrying Value		Fair Value
Credit Agreement (carrying value including current maturities)	$	150	$	163	$	190	$	201
Convertible debt (par value)		150		158		150		140

Allowance for doubtful accounts receivable

The activity in our allowance for doubtful accounts receivable is as follows (in thousands):

	2012			2011			2010
Balance, beginning of year	$	2,421		$	1,837		$	2,036
Additions (reductions) to expense		1,039			844			(58	)
Write-offs		(174	)		(239	)		(103	)
Other		(139	)		(21	)		(38	)
Balance, end of year	$	3,147		$	2,421		$	1,837

Net Income attributed to Common Stock and Participating Restricted Common Stock

The amounts attributed to both common stock and participating restricted stock used as the numerators in both the basic and diluted EPS calculations are as follows (in thousands):

	2012		2011		2010
Net income attributed to:
Common stock	$	48,853	$	42,040	$	22,061
Participating restricted stock		26		242		368
Total	$	48,879	$	42,282	$	22,429

Calculation of the Denominator of the Basic and Diluted Earnings (Loss) per Share (EPS) computations

The weighted-average shares outstanding used in the basic and diluted EPS denominators related to common stock and participating restricted stock are as follows (in thousands):

	2012		2011		2010
Weighted-average shares outstanding – Basic:
Common stock		32,142		32,624		32,537
Participating restricted stock		17		189		543
Total		32,159		32,813		33,080
Weighted-average shares outstanding – Diluted:
Common stock		32,459		32,833		32,822
Participating restricted stock		17		189		543
Total		32,476		33,022		33,365

Reconciliation of the basic and diluted EPS denominators

The reconciliation of the basic and diluted EPS denominators related to the common shares is included in the following table (in thousands):

	2012		2011		2010
Basic weighted-average common shares		32,142		32,624		32,537
Dilutive effect of common stock options		11		19		24
Dilutive effect of unvested restricted stock		306		190		261
Dilutive effect of 2010 Convertible Notes		—		—		—
Diluted weighted-average common shares		32,459		32,833		32,822