Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss
Balance at beginning of period at Dec. 31, 2014	$ 1,580,070	$ 129,796	$ 1,665	$ 897,049	$ 1,992,833	$ (1,375,322)	$ (65,951)
Increase (Decrease) in Stockholders' Equity
Net income	19,307				19,307
Other comprehensive income, net of tax	2,491						2,491
Dividends on preferred stock	(2,194)				(2,194)
Dividends on common stock	(3,995)				(3,995)
Sales of treasury stock	6,009				(3,739)	9,748
Restricted stock grants				(330)	(212)	542
Forfeitures of restricted stock				478	378	(856)
Stock-based compensation	1,608			1,597	11
Net tax benefit excess (shortfall) from stock-based compensation	(6)			(6)
Balance at end of period at Mar. 31, 2015	1,603,290	129,796	1,665	898,788	2,002,389	(1,365,888)	(63,460)
Balance at beginning of period at Dec. 31, 2015	1,663,448	129,796	1,665	902,349	2,045,391	(1,357,136)	(58,617)
Increase (Decrease) in Stockholders' Equity
Net income	18,565				18,565
Other comprehensive income, net of tax	4,410						4,410
Dividends on preferred stock	(2,194)				(2,194)
Dividends on common stock	(4,053)				(4,053)
Sales of treasury stock	41				(15)	56
Restricted stock grants				(10,329)	(3,823)	14,152
Forfeitures of restricted stock				45	25	(70)
Stock-based compensation	1,581			1,580	1
Net tax benefit excess (shortfall) from stock-based compensation	3			3
Balance at end of period at Mar. 31, 2016	$ 1,681,801	$ 129,796	$ 1,665	$ 893,648	$ 2,053,897	$ (1,342,998)	$ (54,207)