Earnings Per Share ("EPS") (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income		$ 53,562	$ 23,065	$ 104,874	$ 45,185
Average common shares outstanding (in shares)		92,264	63,633	92,223	63,170
Average potential dilutive common shares (in shares)		469	418	469	418
Average diluted common shares (in shares)		92,733	64,051	92,692	63,588
Basic earnings per share (in dollars per share)	[1]	$ 0.58	$ 0.36	$ 1.14	$ 0.72
Diluted earnings per share (in dollars per share)	[1]	$ 0.58	$ 0.36	$ 1.13	$ 0.71

[1] All per share amounts have been restated to reflect the effect of the two-for-one stock split on February 8, 2018.