Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income available to common stockholders	$ 34,392	$ 33,849	$ 44,869	$ 53,512
Weighted average common shares outstanding, basic (in shares)	48,070	48,017	48,058	48,007
Weighed average common shares outstanding, dilutive (in shares)	48,070	48,017	48,058	48,007
Earnings per share - basic (in dollars per share)	$ 0.72	$ 0.70	$ 0.93	$ 1.11
Earnings per share - diluted (in dollars per share)	$ 0.72	$ 0.70	$ 0.93	$ 1.11