CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	16,670,000	16,670,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	100,000,000	100,000,000
Common stock, issued (in shares)	67,287,231	66,258,559
Common stock, outstanding (in shares)	67,287,231	66,258,559
Redeemable Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	5,409,650	0
Preferred stock, dividend rate	7.25%	7.25%
Preferred stock, liquidation preference (in dollars per share)	$ 25	$ 25
Preferred stock, issued (in shares)	5,409,650	0
Preferred stock, outstanding (in shares)	5,409,650	0