Earnings Per Share. The table that follows presents our computation of weighted average basic and diluted shares outstanding, which we use in our earnings per share calculations. For each period presented, our net income allocable to both common shareholders and diluted common shareholders is the same as our net income in our consolidated statements of income.



	Three Months Ended March 31,
(in thousands)	2013	2012
Basic shares outstanding	108,037	108,155
Effect of restricted stock units	575	606
Diluted shares outstanding	108,612	108,761

Share-Based Compensation. We have no outstanding stock options and no future share-based compensation to be recognized pursuant to stock option grants.

We grant restricted units of our common stock to certain of our key executives, key employees and Chairman of the Board. We also grant shares of restricted stock to our other non-employee directors. The restricted units granted to our key executives and key employees generally vest in full on the third anniversary of the award date, conditional on continued employment. The restricted unit grants, including those granted to our Chairman, can vest pro rata over three years, provided the individual meets certain age and years-of-service requirements. We grant shares of restricted common stock to our other non-employee directors. These shares vest in full on the first anniversary of the award date, conditional upon continued service as a director.

For each of the restricted stock units granted in 2011 through 2013, at the earlier of three years after grant or at termination of employment or service, the grantee will be issued a share of our common stock for each common stock unit vested. As of March 31, 2013 and December 31, 2012, totals of 988,426 and 1,031,572 shares of restricted stock or restricted stock units were outstanding. Each grantee of shares of restricted stock is deemed to be the record owner of those shares during the restriction period, with the right to vote and receive any dividends on those shares. The restricted stock units outstanding have no voting or dividend rights.

We estimate that stock-based compensation cost not yet recognized related to shares of restricted stock or restricted stock units, based on their grant-date fair values, was $29 million at March 31, 2013. This expense is being recognized on a staged-vesting basis over three years for awards attributable to individuals meeting certain age and years-of-service requirements, and on a straight-line basis over the applicable vesting period of one or three years for the other awards.

Share Repurchase Plan. In February 2010, our Board of Directors approved a plan to repurchase up to 12 million shares of our common stock. Through March 31, 2013, under this plan, we had repurchased 3.1 million shares of our common stock for $86 million.