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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Computation of basic and diluted loss per share
Net income available to common shareholders	$ 25,874	$ 17,862	$ 73,414	$ 53,328
Weighted average shares outstanding:
Basic (in shares)	71,556	66,294	71,992	63,297
Effect of dilutive securities
Stock options	5	6	4	5
Diluted (in shares)	71,561	66,300	71,996	63,302
Net income per common share:
Basic (in dollars per share)	$ 0.36	$ 0.27	$ 1.02	$ 0.84
Diluted (in dollars per share)	$ 0.36	$ 0.27	$ 1.02	$ 0.84