Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Statement Of Stockholders Equity [Abstract]
Common treasury shares (in shares)	43,095,635	45,452,865	43,095,635	45,452,865	43,483,398	45,243,329	45,465,877	45,813,109
Cash dividends declared per common share (in dollars per share)		$ 0.00		$ 0.16