Stock-based Compensation

3 Months Ended

Mar. 31, 2012

Stock-based Compensation [Abstract]

Stock-based Compensation

(8) Stock-Based Compensation

 The Company's stock-based compensation expense for the three months ended March 31, 2012 included performance-based restricted stock units (PRSUs), non-qualified stock options, restricted stock units (RSUs) and deferred stock units (DSUs). A summary of the Company's stock-based compensation expense for the three months ended March 31, 2012 and 2011 is presented below:

		March 31, 2012		March 31, 2011
PRSU expense	$	2,701	$	877
Option expense		1,128		1,358
RSU/DSU expense		533		494
Total stock-based compensation expense	$	4,362	$	2,729

 A summary of the Company's PRSU activity and related information for the three months ended March 31, 2012 is presented below:

	Number of Shares		Weighted-Average Grant Date Fair Value		Aggregate Intrinsic Value
Awards outstanding at December 31, 2011	285	$	37.93
Granted	134		71.52
Vested	-		-
Forfeited	-		-
Awards outstanding at March 31, 2012	419	$	48.67	$	35,359

 The maximum number of shares to be awarded under the PRSUs granted during the three months ended March 31, 2012 and 2011 will be 403 and 443 shares, and will vest, if earned, at the end of the three-year performance periods ending on December 31, 2013 and 2012, respectively.

 A summary of the Company's stock option activity and related information for the three months ended March 31, 2012 is presented below:

	Number of Shares			Weighted-Average Grant Date Fair Value	Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Options outstanding December 31, 2011	3,408		$	11.15
Granted	88			71.17
Forfeited	-			-
Exercised	(494	)		14.82
Options outstanding at March 31, 2012	3,002		$	15.06	6.43	$	208,134
Options exercisable at March 31, 2012	2,019		$	13.75	6.08	$	142,704

 The aggregate intrinsic value of options exercised during the three months ended March 31, 2012 and 2011 was $34,387 and $35,926, respectively.

 No RSUs or DSUs were granted during the three months ended March 31, 2012.

 A summary of total unrecognized stock-based compensation expense based on current performance estimates related to the PRSUs and options granted during the three months ended March 31, 2012 is presented below:

		March 31, 2012	Weighted-Average Remaining Vesting Period
Unrecognized PRSU expense	$	9,152	2.86
Unrecognized stock option expense		2,965	2.84
Total unrecognized stock-based compensation expense	$	12,117	2.85