Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
TREASURY STOCK, AT COST:
Purchases, shares	710,000	1,680,000	5,850,000
RETAINED EARNINGS:
Cash dividends declared on common stock, per share	$ 1.98	$ 3.58	$ 3.09