Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	300,000,000	300,000,000
Common stock, issued (in shares)	139,599,454	139,530,654
Common stock outstanding (in shares)	139,588,782	139,530,654
Treasury stock (in shares)	10,672	0