Capital Stock (Tables)

12 Months Ended

Dec. 31, 2020

Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]

Common Shares Outstanding and Treasury Shares Held Rollforward Table

Common Shares Outstanding	Year Ended December 31,
	2020	2019	2018
At beginning of period	125,481,163	125,737,565	115,877,704
Exercise of common stock options, net	—	—	65,524
Grants of restricted stock, net (1)	494,908	(256,402)	2,022,316
Issuance of common stock	—	—	7,772,021
At end of period	125,976,071	125,481,163	125,737,565

(1)Prior to 2019, we primarily granted restricted stock awards, which immediately impacted common shares outstanding. In contrast, during 2020 and 2019, we primarily granted restricted stock units which do not impact common shares outstanding until vesting. Vesting for restricted stock units began in 2020.

Treasury Shares Held	Year Ended December 31,
	2020	2019	2018
At beginning of period	2,823,191	2,717,569	2,638,093
Shares received upon vesting of restricted stock, net	130,785	105,622	79,476
At end of period	2,953,976	2,823,191	2,717,569