	Year ended December 31,
	2018			2017			2016
	(In thousands)
Common stock, beginning of period		44,251			45,721			48,297
Shares issued for stock options exercised		33			38			148
Shares of common stock issued upon lapse of RSUs		528			504			516
Common stock retired		(2,118	)		(2,012	)		(3,240	)
Common stock, end of period		42,694			44,251			45,721

The above reconciliation excludes RSUs and PSUs, which do not have voting rights. As sales restrictions on RSUs lapse and PSUs are earned, we issue common shares with voting rights. As of December 31, 2018, we had a total of 576,992 RSUs and 85,010 PSUs outstanding. The PSU outstanding balance is based on the targeted number of PSUs outlined in the award agreement; however, the actual number of PSUs that vest could be higher or lower based on actual versus targeted performance. See Note 14 (Share Based Transaction) for a discussion of the PSU award structure.

On February 6, 2018, our Board of Directors authorized a share repurchase program for up to $275.0 million of our outstanding common stock for purchases through June 30, 2019 (the “share repurchase program”). Under the share repurchase program, we repurchased 2,036,188 shares of our common stock in the open market for an aggregate purchase price of $210.1 million through December 31, 2018. Approximately $65.0 million of our outstanding common stock remains available for repurchases under the share repurchase program as of December 31, 2018. On February 7, 2019, our Board of Directors authorized a new share repurchase program for up to $275.0 million of our outstanding common stock (including $65.0 million remaining from the prior repurchase program) for purchases through June 30, 2020.