Shareholders’ equity

Common Stock

As of June 30, 2018 and December 31, 2017, we had 195,000,000 shares of common stock, $0.01 cent par value per share, authorized under our Restated Certificate of Incorporation, of which 94,787,612 shares were issued and 87,601,091 shares were outstanding at June 30, 2018; 94,731,298 shares were issued and 87,544,777 shares were outstanding at December 31, 2017.

The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of our preferred stock which are currently outstanding, including our Series A Convertible Preferred Stock, or which we may designate and issue in the future.

Preferred Stock

At June 30, 2018 and December 31, 2017 we had 5,000,000 shares of preferred stock, $0.01 cent par value per share, authorized under our Restated Certificate of Incorporation. In 2008, we issued 160,000 shares of our Series A Convertible Preferred Stock. At June 30, 2018 and December 31, 2017, there were 74,123 and 74,364 shares of Series A Convertible Preferred Stock outstanding, respectively, and held by Glencore.

The issuance of common stock under our stock incentive programs, debt exchange transactions and any stock offering that excludes Glencore participation triggers anti-dilution provisions of the preferred stock agreement and results in the automatic conversion of Series A Convertible Preferred Stock shares into shares of common stock. The conversion of preferred to common shares is 100 shares of common for each share of preferred stock. Our Series A Convertible Preferred Stock has a par value of $0.01 per share.

The Common and Preferred Stock table below contains additional information about preferred stock conversions during the six months ended June 30, 2018 and 2017.



	Preferred stock		Common stock
Common and Preferred Stock Activity (in shares):	Series A convertible		Treasury	Outstanding
Beginning balance as of December 31, 2017	74,364		7,186,521	87,544,777
Conversion of convertible preferred stock	(241	)	—	24,167
Issuance for share-based compensation plans	—		—	32,147
Ending balance as of June 30, 2018	74,123		7,186,521	87,601,091

Beginning balance as of December 31, 2016	75,625		7,186,521	87,250,897
Conversion of convertible preferred stock	(279	)	—	27,904
Issuance for share-based compensation plans	—		—	37,164
Ending balance as of June 30, 2017	75,346		7,186,521	87,315,965

Stock Repurchase Program

Our Board of Directors authorized a $60.0 million common stock repurchase program and during the first quarter of 2015, our Board of Directors increased the size of the program by $70.0 million. Under the program, Century is authorized to repurchase up to $130.0 million of our outstanding shares of common stock, from time to time, on the open market at prevailing market prices, in block trades or otherwise. The timing and amount of any shares repurchased will be determined by our management based on its evaluation of market conditions, the trading price of our common stock and other factors. The stock repurchase program may be suspended or discontinued at any time.

Shares of common stock repurchased are recorded at cost as treasury stock and result in a reduction of shareholders’ equity in the consolidated balance sheets. From time to time, treasury shares may be reissued as contributions to our employee benefit plans and for the conversion of convertible preferred stock. When shares are reissued, we use an average cost method for determining the cost. The difference between the cost of the shares and the reissuance price is added to or deducted from additional paid-in capital.

Through June 30, 2018 we had repurchased 7,186,521 shares of common stock for an aggregate purchase price of $86.3 million. We have made no share repurchases since April 2015 and we have $43.7 million remaining under the repurchase program authorization as of June 30, 2018.