CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized net gain on equity securities	$ 0				$ 280	$ (280)
Balance at beginning of period at Dec. 31, 2017	991,457	$ 938	$ 29,953	$ 503,709	481,331	(24,474)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	8,572				23,268	(14,696)
Cash dividends declared:
Series D Preferred, $17.50 per share	(13)				(13)
Common	(3,907)				(3,907)
Purchase of 1,761 shares of common stock	(97)						(97)
Issuance of shares of common stock	53,635		1,115	52,423			97
Stock based compensation	1,858			1,858
Balance at end of period at Mar. 31, 2018	1,051,505	938	31,068	557,990	500,959	(39,450)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification of unrealized net gain on equity securities	(1,713)				(1,713)
Balance at beginning of period at Dec. 31, 2018	1,325,175	0	34,477	743,095	579,252	(31,649)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	51,542				31,497	20,045
Cash dividends declared:
Common	(5,530)				(5,530)
Issuance of shares of common stock	253		127	126
Stock based compensation	2,375			2,375
Balance at end of period at Mar. 31, 2019	$ 1,372,102	$ 0	$ 34,604	$ 745,596	$ 603,506	$ (11,604)	$ 0