Earnings Per Common Share (Earnings per common share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 19,532	$ 19,621	$ 64,588	$ 78,352
Non-Convertible Preferred Stock Dividend (Series A,B and D)	(1,627)	(1,628)	(4,882)	(4,884)
Convertible Preferred Stock Dividend (Series C)	(1,838)	(1,837)	(5,514)	(5,512)
Income available to common shareholders	16,067	16,156	54,192	67,956
Effect of assumed conversion of convertible preferred stock	1,838	1,837	5,514	5,512
Income available to common sharesholders assuming conversion	$ 17,905	$ 17,993	$ 59,706	$ 73,468
Average common shares outstanding	45,055	45,927	45,131	45,717
Average potential common shares options	160	257	162	198
Average potential common shares convertible preferred stock	7,147	7,138	7,147	7,138
Average common shares outstanding and equivalents	52,362	53,322	52,440	53,053
Earnings per common share - basic	$ 0.36	$ 0.35	$ 1.20	$ 1.49
Earnings per common share - diluted	$ 0.34	$ 0.34	$ 1.14	$ 1.39