Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Basic (shares)	103,768,000	100,776,000	102,791,000	92,345,000
Dilutive effect of stock awards (shares)	796,000	744,000	741,000	587,000
Weighted average shares diluted (shares)	104,564,000	101,520,000	103,532,000	92,932,000
Net income available to common shareholders	$ 67,052	$ 55,684	$ 189,998	$ 135,119
Earnings (loss) per share - basic (in dollars per share)	$ 0.65	$ 0.55	$ 1.85	$ 1.46
Earnings (loss) per share - diluted (in dollars per share)	$ 0.64	$ 0.55	$ 1.84	$ 1.45
Anti-dilutive stock options outstanding that were not included in computation of diluted earnings per common share (shares)	0	0	0	0