Equity (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Rollforward of Common Stock

A summary of the outstanding shares of common stock is as follows:

Balance as of January 1, 2017	794,960,092
Exercise of stock options	617,612
Issuance of restricted stock	37,270
Vesting of restricted stock units	64,150
Repurchase of common stock	(6,194,137	)
Balance as of December 31, 2017	789,484,987
Exercise of stock options	1,007,551
Issuance of restricted stock	10,296
Vesting of restricted stock units	5,000
Repurchase of common stock	(15,044,620	)
Balance as of December 31, 2018	775,463,214
Exercise of stock options	569,224
Issuance of restricted stock	11,039
Repurchase of common stock	(12,558,562	)
Balance as of December 31, 2019	763,484,915