Earnings Per Share - Computation of basic and diluted earnings per share (Details 1) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Computation of basic and diluted loss per share
Net income available to common shareholders	$ 25,266	$ 17,796	$ 47,540	$ 35,466
Weighted average shares outstanding:
Basic	72,202	62,549	72,187	61,730
Effect of dilutive securities
Stock options	5	4	4	4
Diluted	72,207	62,553	72,191	61,734
Net income per common share:
Basic (in dollars per share)	$ 0.35	$ 0.28	$ 0.66	$ 0.57
Diluted (in dollars per share)	$ 0.35	$ 0.28	$ 0.66	$ 0.57