CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000	500,000
Common stock, shares issued	137,279	138,869