Condensed Consolidated Statement of Shareholders' Equity - 6 months ended Jun. 30, 2016 - USD ($) $ in Thousands	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Shares [Member]
Shares Outstanding, Beginning Balance at Dec. 31, 2015		2,000	24,649,044
Stockholders' Equity, Beginning Balance at Dec. 31, 2015	$ 596,566	$ 48,163	$ 271	$ 241,239	$ 355,427	$ (48,534)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	25,105				25,105
Dividends, Preferred Stock	(2,438)				(2,438)
Reversal of deferred tax asset related to stock options and executive deferred compensation distributions	(1,030)			(1,030)
Stock options exercised, shares			6,000
Stock options exercised	73			(46)		119
Stock-based compensation expense	2,126			2,126
Deferral of executive and director compensation	110			110
Executive and director deferred compensation distributions shares			13,789
Executive and director deferred compensation distributions	0			(274)		274
Shares Outstanding, Ending Balance at Jun. 30, 2016		2,000	24,668,833
Stockholders' Equity, Ending Balance at Jun. 30, 2016	$ 620,512	$ 48,163	$ 271	$ 242,125	$ 378,094	$ (48,141)