Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares	3 Months Ended						12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 30, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Cash dividends declared per share	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.18	$ 0.36	$ 0.45