14.   STOCK-BASED COMPENSATION

Stock Compensation Plans

Stock options and time lapse restricted shares (TLRSs) have been issued to officers and other management employees under the Company's Employee Stock Incentive Plan.

Stock Options

The Company's stock options generally vest over a five-year period and expire ten years from the issuance date. For the year ended December 31, 2012, the Company issued approximately 32 thousand shares of common stock upon exercise of stock options by employees and issued 0.1 million shares in 2011.

In order to estimate the fair value of stock options, the Company used the Black-Scholes option valuation model, which was developed for use in estimating the fair value of publicly traded options, which have no vesting restrictions and are fully transferable. Option valuation models require the input of highly subjective assumptions and these assumptions can vary over time.

Option activity under the Company's stock option plan as of December 31, 2012, 2011 and 2010 and changes during the year ended December 31, 2012 were as follows:

The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value (the difference between the Company's closing stock price on the last trading day of the year and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on that day. The amount of aggregate intrinsic value will change based on the fair market value of the Company's stock.

The aggregate intrinsic value of options exercised during the years ended December 31, 2012, 2011 and 2010 was $0.5 million, $1.7 million and $5.2 million, respectively. Exercise of options during the years ended December 31, 2012, 2011 and 2010 resulted in cash receipts of less than $1 thousand, $0.1 million and $0.3 million, respectively.

Time Lapse Restricted Shares and Restricted Stock Units

TLRSs provide for the issuance of a share of the Company's Common Stock at no cost to the holder and generally vest after a certain stipulated number of years from the grant date, depending on the terms of the issue. The Company issued TLRSs that vest over ten years prior to 2004. TLRSs issued 2004 and later vest in 20 percent increments starting with the second anniversary of the grant, over six years from the date of grant. During these years, grantees receive all dividends declared and retain voting rights for the granted shares. The agreements under which the restricted stock is issued provide that shares awarded may not be sold or otherwise transferred until restrictions established under the plans have lapsed.

The Company issued time lapse restricted shares of 0.8 million, 0.7 million and 0.9 million for the years ended December 31, 2012, 2011 and 2010, respectively.

The Company issues new shares from its authorized but unissued share pool. At December 31, 2012, approximately 4.5 million shares of the Company's common stock were reserved for issuance. In accordance with FASB ASC Topic 718, "Compensation—Stock Compensation," the Company uses the modified prospective application method of adoption, which requires the Company to record compensation cost, related to unvested stock awards as of December 31, 2005 by recognizing the unamortized grant date fair value of these awards over the remaining service periods of those awards with no change in historical reported earnings. Awards granted after December 31, 2005 are valued at fair value and recognized on a straight line basis over the service periods of each award. The Company estimates restricted share forfeiture rates based on its historical experience.

The following table summarizes the components of the Company's stock-based compensation programs recorded as expense ($ in thousands):

As of December 31, 2012 and 2011, $30.9 million and $24.4 million, respectively, of total unrecognized compensation cost related to time-lapse restricted shares is expected to be recognized over a weighted average period of approximately 4.1 years at December 31, 2012, 2011 and 2010, respectively.

The following table summarizes information on unvested restricted stock units outstanding as of December 31, 2012, 2011 and 2010: