Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Treasury stock (in shares)	3,437	6,833
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	160,000,000	120,000,000
Common stock, shares issued (in shares)	108,513,597	99,518,764
Common stock, shares outstanding (in shares)	108,510,160	99,511,931