Equity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Changes in total common stockholders' equity
Balance at the beginning of the period	$ 642,155
Common stock issued	1
Share-based compensation expense	333
Shares purchased back	(466)
Common stock dividends declared	(8,258)
Net (loss) income	(798)	$ 1,575
Balance at the end of the period	$ 632,967