Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Common Stock and Additional Paid-in Capital	Retained Earnings	Treasury Stock	AOCI, net of tax
BALANCE (in shares) at Dec. 31, 2015		143,909,233
Beginning balance at Dec. 31, 2015	$ 3,122,950		$ 1,701,459	$ 1,872,594	$ (436,162)	$ (14,941)
Increase (Decrease) in Stockholders' Equity
Net income	107,516			107,516
Other comprehensive income	12,883					12,883
Stock compensation costs	4,575		4,575
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)		154,518
Net activity of common stock pursuant to various stock compensation plans and agreements	(2,068)		986		(3,054)
Common stock dividends	(29,075)			(29,075)
BALANCE (in shares) at Mar. 31, 2016		144,063,751
Ending balance at Mar. 31, 2016	3,216,781		1,707,020	1,951,035	(439,216)	(2,058)
BALANCE (in shares) at Dec. 31, 2016		144,167,451
Beginning balance at Dec. 31, 2016	3,427,741		1,727,598	2,187,676	(439,387)	(48,146)
Increase (Decrease) in Stockholders' Equity
Net income	169,736			169,736
Other comprehensive income	4,628					4,628
Stock compensation costs	5,151		5,151
Net activity of common stock pursuant to various stock compensation plans and agreements (in shares)		294,115
Net activity of common stock pursuant to various stock compensation plans and agreements	(12,154)				(12,154)
Common stock dividends	(29,148)			(29,148)
BALANCE (in shares) at Mar. 31, 2017		144,461,566
Ending balance at Mar. 31, 2017	$ 3,565,954		$ 1,732,749	$ 2,328,264	$ (451,541)	$ (43,518)