Consolidated Statement of Changes in Stockholders' Equity - Unaudited (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Cumulative-effect of change in accounting principle related to credit losses					ASU 2016-13
Dividends declared per common share (in dollars per share)	$ 0.330	$ 0.275	$ 0.990	$ 0.825