Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Stockholders Equity [Abstract]
Cash dividends declared per common share	$ 0.60	$ 0.60	$ 0.60	$ 0.51	$ 0.51	$ 0.51	$ 1.80	$ 1.53