CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	260,000,000	260,000,000
Common stock, shares issued	170,552,890	169,644,644
Common stock, shares outstanding	159,854,695	165,354,180
Treasury stock, shares	10,698,195	4,290,527