Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 40,821	$ 25,070	$ 112,852	$ 59,631
Net income available to common shareholders	$ 40,821	$ 25,070	$ 112,852	$ 59,631	$ 88,497
Basic earnings per share (in dollars per share)	$ 0.45	$ 0.30	$ 1.25	$ 0.72
Diluted earnings per share (in dollars per share)	$ 0.44	$ 0.29	$ 1.23	$ 0.70
Basic weighted average shares outstanding (in shares)	90,418	83,640	90,317	83,263
Dilutive effect of nonvested shares (in shares)	1,423	1,388	1,361	1,548
Diluted weighted average shares outstanding (in shares)	91,841	85,028	91,678	84,811