Basis of Presentation (Earnings per share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share
Net income	$ 21,632	$ 20,208	$ 61,600	$ 61,187
Preferred dividends and discount	(13)	(53)	(45)	(273)
Interest expense on convertible preferred debt	3	17	12	48
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 21,622	$ 20,172	$ 61,567	$ 60,962
Weighted average common shares outstanding for basic earnings per share (in shares)	29,648	24,601	27,569	24,262
Assumed incremental common shares issued upon exercise of stock options and non-vested restricted stock units (in shares)	262	322	265	319
Weighted average common shares for diluted earnings per share (in shares)	29,910	24,923	27,834	24,581
Earnings per common share — basic (in dollars per share)	$ 0.73	$ 0.82	$ 2.23	$ 2.51
Earnings per common share — diluted (in dollars per share)	$ 0.72	$ 0.81	$ 2.21	$ 2.48
Number of antidilutive common stock equivalents excluded from diluted earnings per share computation (in shares)	0	0	0	0