Share-Based Compensation

6 Months Ended

Jun. 30, 2012

Share-Based Compensation

12. Share-Based Compensation

Our stock compensation plans permit the grant of incentive and nonqualified stock options, common stock, deferred common stock units, restricted stock and restricted stock units to our employees and directors. Generally, stock options granted under our stock compensation plans vest over a three-year period, with one-third vesting in each year. Common stock and deferred common stock units granted under our stock compensation plans vest immediately, and we recognize compensation expense related to those grants on the grant date. Restricted stock and restricted stock units granted under our stock compensation plans vest over a three-year period, either at the end of the three years or with one-third vesting in each year. We recognize compensation expense related to our stock compensation plans in the General and administrative expenses caption on our Condensed Consolidated Statements of Operations.

Equity-Classified Awards

Most of the awards issued under our stock compensation plans are classified as equity instruments because they result in the issuance of common stock on the date of grant, upon exercise or are otherwise payable in common stock upon vesting, as applicable. The recognition of compensation cost attributable to these awards is a non-cash item of expense.

Liability-Classified Awards

In February 2012, we granted performance-based restricted stock units (“PBRSUs”) to certain executive officers. Vested PBRSUs are payable in cash on the third anniversary of the date of grant based upon the achievement of certain market-based performance metrics with respect to each of a one-year, two-year and three-year performance period, in each case commencing on the date of grant. The number of PBRSUs vested can range from 0% to 200% of the initial grant. The PBRSUs do not have voting rights and do not participate in dividends.

Because the PBRSUs are payable in cash, they are considered liability-classified awards and are included in the Other liabilities caption on our Condensed Consolidated Balance Sheets. Compensation cost associated with the PBRSUs is measured at the end of each reporting period based on the fair value derived from a Monte Carlo model and recognized based on the period of time that has elapsed during each of the individual performance periods.

 The following table summarizes share-based compensation expense recognized for the periods presented:

	Three Months Ended June 30,				Six Months Ended June 30,
	2012		2011		2012		2011
Equity-classified awards:
Stock option plans	$	950	$	1,379	$	2,158	$	2,787
Common, deferred, restricted and time-based restricted unit plans	386		634		793		1,022
	1,336		2,013		2,951		3,809
Liability-classified awards	553		—		625		—
	$	1,889	$	2,013	$	3,576	$	3,809