CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Accumulated depreciation	$ 402,338	$ 340,423
Equity
Preferred stock, par value (in dollars per share)		$ 0.01
Preferred stock, shares authorized		10,000,000
Preferred stock, shares issued		5,750,000
Preferred stock, shares outstanding		5,750,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	178,306,528	178,255,843
Common stock, shares outstanding	178,306,528	178,255,843