CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Preferred Stock	Surplus	Retained earnings	Treasury Stock	Accumulated other comprehensive income (loss)
Beginning Balance at Dec. 31, 2016	$ 5,197,957	$ 1,040	$ 50,160	$ 4,255,022	$ 1,220,307	$ (8,286)	$ (320,286)
Net Income	189,171				189,171
Issuance of stock	3,831	1		3,830
Dividends declared:
Dividends, Common Stock, Cash	(51,112)				(51,112)
Dividends, Preferred Stock, Cash	(1,862)				(1,862)
Common stock purchases	(77,283)			4,518		(81,801)
Other comprehensive loss, net of tax	17,343						17,343
Ending Balance at Jun. 30, 2017	5,278,045	1,041	50,160	4,263,370	1,356,504	(90,087)	(302,943)
Beginning Balance at Dec. 31, 2017	5,103,905	1,042	50,160	4,298,503	1,194,994	(90,142)	(350,652)
Net Income	371,107				371,107
Issuance of stock	1,743	1		1,742
Dividends declared:
Dividends, Common Stock, Cash	(51,116)				(51,116)
Dividends, Preferred Stock, Cash	(1,862)				(1,862)
Common stock purchases	(2,344)					(2,344)
Common stock reissuance	1,337			40		1,297
Stock based compensation	11,096			2,661		8,435
Other comprehensive loss, net of tax	(146,140)						(146,140)
Ending Balance at Jun. 30, 2018	5,289,661	$ 1,043	$ 50,160	$ 4,302,946	1,515,058	$ (82,754)	$ (496,792)
Cumulative effect of accounting change	$ 1,935				$ 1,935