(10)	Capital Stock

We have authorized capital stock of 485.0 million shares, which includes 475.0 million shares of common stock and 10.0 million shares of preferred stock. The following is a schedule of changes in the number of common shares outstanding since the beginning of 2015:


	Year Ended December 31,
	2017		2016			2015
Beginning balance		247,144,356		169,316,460			168,628,177
MRD Merger		—		77,042,749			—
Stock options/SARs exercised		—		—			77,002
Restricted stock grants		539,096		490,609			335,103
Restricted stock units vested		344,937		266,541			252,507
Performance stock units issued		85,461		—			—
Shares retired		—		(739	)		—
Treasury shares		15,580		28,736			23,671
Ending balance		248,129,430		247,144,356			169,316,460

Common Stock Dividends

The board of directors declared quarterly dividends of $0.02 per common share for each of the four quarters of 2017 and 2016. The board of directors declared quarterly dividends of $0.04 per common share for each of the four quarters of 2015. The determination of the amount of future dividends, if any, to be declared and paid is at the sole discretion of the board of directors and will depend on our financial condition, earnings, capital requirements, levels of indebtedness, our future business prospects and other matters our board of directors deem relevant. Our bank credit facility and our senior subordinated notes allow for the payment of common dividends, with certain limitations.