Consolidated Statements of Changes in Stockholders' Equity (USD $)	Series B Preferred Stock [Member] Preferred Stock [Member]	Series B Preferred Stock [Member] Additional Paid-in Capital [Member]	Series B Preferred Stock [Member] Parent [Member]	Series B Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member] Restricted Stock Units (RSUs) [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Parent [Member] Restricted Stock Units (RSUs) [Member]	Parent [Member]	Total
Balance at December 31 at Dec. 31, 2011					$ 250,992,000	$ 829,000		$ 765,641,000	$ (8,732,000)	$ 624,192,000	$ (125,736,000)	$ 8,447,000		$ 1,515,633,000
Balance at December 31 (in Shares) at Dec. 31, 2011					258,000	78,652,557
Dividend Reinvestment Plan								291,000						291,000	291,000
Dividend Reinvestment Plan (in Shares)						17,956									17,956
Restricted stock units vested (in Shares)						11,814
Stock salary								788,000						788,000
Stock salary (in Shares)						45,937									45,937
Stock options exercised						1,000		763,000						764,000
Stock options exercised (in Shares)						50,024									50,024
Tax short-fall from stock options								(620,000)						(620,000)
Stock -based compensation								2,062,000						2,062,000
Cash dividends										(3,149,000)				(3,149,000)
Adjustment on preferred stock					3,588,000					(3,588,000)
Dividends on preferred stock										(12,900,000)		(605,000)		(13,505,000)	(16,488,000)
Change in other comprehensive loss									9,197,000					9,197,000
Net income										117,438,000		605,000		118,043,000	117,438,000
Balance at December 31 at Dec. 31, 2012					254,580,000	830,000		768,925,000	465,000	721,993,000	(125,736,000)	8,447,000		1,629,504,000
Balance at December 31 (in Shares) at Dec. 31, 2012					258,000	78,778,288
Dividend Reinvestment Plan								605,000						605,000	605,000
Dividend Reinvestment Plan (in Shares)						25,984									25,984
Redemption of Series B Preferred Stock	(258,000,000)	(302,000)	(258,302,000)	(258,000,000)
Redemption of Series B Preferred Stock (in Shares)	(258,000)
Redemption of noncontrolling interest								(191,000)				(8,447,000)		(8,638,000)
Restricted stock units vested						1,000								1,000
Restricted stock units vested (in Shares)						138,220
Stock salary						1,000		1,106,000						1,107,000
Stock salary (in Shares)						52,431									52,431
Stock options exercised						6,000		14,749,000						14,755,000
Stock options exercised (in Shares)						594,946									594,946
Tax short-fall from stock options								(2,509,000)						(2,509,000)
Stock -based compensation								2,106,000						2,106,000
Cash dividends										(6,342,000)				(6,342,000)
Adjustment on preferred stock					3,420,000					(3,420,000)
Dividends on preferred stock										(6,265,000)		(592,000)		(6,857,000)	(9,685,000)
Change in other comprehensive loss									(30,194,000)					(30,194,000)
Net income										123,143,000		592,000		123,735,000	123,143,000
Balance at December 31 at Dec. 31, 2013						838,000		784,489,000	(29,729,000)	829,109,000	(125,736,000)			1,458,971,000
Balance at December 31 (in Shares) at Dec. 31, 2013						79,589,869
Dividend Reinvestment Plan						1,000		2,847,000						2,848,000	2,800,000
Dividend Reinvestment Plan (in Shares)						116,957									116,957
Restricted stock units vested						1,000								1,000
Restricted stock units vested (in Shares)						88,537
Shares withheld related to net share settlement of RSUs							(850,000)						(850,000)
Stock issued to directors								350,000						350,000
Stock issued to directors (in Shares)						13,690
Stock options exercised								128,000						128,000
Stock options exercised (in Shares)						5,500									5,500
Tax short-fall from stock options								(1,285,000)						(1,285,000)
Stock -based compensation								3,840,000						3,840,000
Cash dividends										(23,105,000)				(23,105,000)
Change in other comprehensive loss									24,160,000					24,160,000
Net income										137,830,000				137,830,000	137,830,000
Balance at December 31 at Dec. 31, 2014						$ 840,000		$ 789,519,000	$ (5,569,000)	$ 943,834,000	$ (125,736,000)			$ 1,602,888,000
Balance at December 31 (in Shares) at Dec. 31, 2014						79,814,553