Stockholders' Equity (Notes)

12 Months Ended

Dec. 31, 2019

Common Stock

The following table shows the beginning and ending balances of our issued and outstanding common stock for the year ended December 31, 2019, 2018, and 2017:



	Year Ended December 31,
	2019		2018		2017
Shares issued and outstanding, beginning balance	70,596,559		69,818,392		69,015,690
Issuance of common stock from vested restricted stock units	1,036,119		1,634,271		1,020,352
Issuance of common stock from exercise of stock options	187,504		617,157		1,441,957
Issuance of common stock for employee stock purchase plan	207,324		175,966		224,928
Repurchase of common stock	(2,510,376	)	(1,190,995	)	(1,549,434	)
Awards effectively repurchased for required employee withholding taxes	(451,639	)	(458,232	)	(335,101	)
Shares issued and outstanding, ending balance	69,065,491		70,596,559		69,818,392

Stock Repurchases

On February 6, 2019, our board of directors authorized a $300 million incremental increase to our ongoing stock repurchase program. This repurchase authorization has no expiration. We retire shares in the period they are acquired and account for the payment as a reduction to stockholders' equity.

The following table summarizes the share repurchases under this program for the years ended December 31, 2019, 2018 and 2017:



	Year Ended December 31,
(in millions, except per share data)	2019		2018		2017
Total cost	$	140	$	61	$	44
Total shares	2,510,376		1,190,995		1,549,434
Average price per share	$	55.64	$	51.22	$	34.46

As of December 31, 2019, $236 million remains available for repurchase under all authorizations approved by the board of directors.