CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity:
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	300,000,000.0	300,000,000
Common stock, shares issued (in shares)	99,200,000	99,200,000
Treasury stock, shares (in shares)	45,400,000	44,700,000