Consolidated Statements of Changes in Shareholders' Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Stockholders Equity [Abstract]
Dividends per common share	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.39	$ 0.39