Consolidated Statement of Stockholders' Equity - USD ($)		Total	Common Stock [Member]	Shares Of Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Dividends declared per share (usd per share)		$ 2.00
Shares, Outstanding at Dec. 31, 2015			121,413,727
Total stockholders' equity at Dec. 31, 2015		$ 4,397,691,000	$ 1,228,000		$ 4,405,775,000	$ 13,907,000	$ (51,047,000)	$ 27,828,000
Net Income		352,166,000				352,166,000
Other comprehensive loss		(21,846,000)						(21,846,000)
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			664,135
net of shares forfeited		23,319,000	$ 7,000		23,312,000
Restricted stock surrendered, shares			(141,358)
Stock Repurchase Program		(5,313,000)					(5,313,000)
Dividend reinvestment, shares			(652,835)
Dividend reinvestment		(27,931,000)			27,924,000
restricted stock		4,406,000			4,406,000
Common stock, $2.30/share		(243,437,000)			(243,437,000)
Total stockholders' equity at Dec. 31, 2016		$ 4,479,055,000	$ 1,228,000		4,162,132,000	366,073,000	(56,360,000)	5,982,000
Shares, Outstanding at Dec. 31, 2016			121,283,669
Dividends declared per share (usd per share)		$ 2.00
Net Income		$ 357,818,000				357,818,000
Other comprehensive loss		25,189,000						25,189,000
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			470,855
net of shares forfeited		25,568,000	$ 5,000		25,563,000
Restricted stock surrendered, shares			(188,870)	2,081,227
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		21,000
Stock Repurchase Program		(9,476,000)					(9,476,000)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		99,677,000			99,656,000		0
Common stock, $2.30/share		(247,403,000)			(247,403,000)
Total stockholders' equity at Dec. 31, 2017		$ 4,977,598,000	$ 1,305,000		4,287,487,000		(65,836,000)	31,171,000
Shares, Outstanding at Dec. 31, 2017			128,782,878
Dividends declared per share (usd per share)		$ 2.30
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	[1]	$ 0			0	(6,136,000)
Net Income		465,339,000				465,339,000
Other comprehensive loss		(43,382,000)						$ (43,382,000)
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			437,831
net of shares forfeited		29,768,000	$ 4,000		29,764,000
Restricted stock surrendered, shares			(181,642)	(5,849,234)
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		(58,000)
Stock Repurchase Program							(9,149,000)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		(306,393,000)
Common stock, $2.30/share		(288,193,000)			$ (288,193,000)
Total stockholders' equity at Dec. 31, 2018		$ 4,825,588,000	$ 1,251,000			1,182,674,000	$ (74,985,000)
Shares, Outstanding at Dec. 31, 2018			123,189,833
Cumulative Effect of New Accounting Principle in Period of Adoption						$ (529,000)

[1] Impact due to adoption on January 1, 2017 of ASU 2016-09, "Improvements to Employee Share-Based Payment Accounting."