Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		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)		$ 1.35
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	[1]	$ 0						$ 6,136
Shares, Outstanding at Dec. 31, 2017			128,782,878
Total stockholders' equity at Dec. 31, 2017		4,977,598	$ 1,305		$ 4,287,487	$ 723,471	$ (65,836)	31,171
Net Income		465,339				465,339
Other comprehensive income		(43,382)						(43,382)
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			437,831
net of shares forfeited		29,768	$ 4		29,764
Restricted stock surrendered, shares			(181,642)
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		58
Stock Repurchase Program		(9,149)					(9,149)
Dividend reinvestment, shares			(5,849,234)
Dividend reinvestment		(306,393)			306,335
Common stock, $1.35/share		(288,193)			(288,193)
Total stockholders' equity at Dec. 31, 2018		4,825,588	$ 1,251		3,722,723	1,182,674	(74,985)	(6,075)
Shares, Outstanding at Dec. 31, 2018			123,189,833
New Accounting Pronouncement Or Change In Accounting Principle Effect Of Change of Income Taxes	[1]					(6,136)
Shares, Outstanding at Dec. 31, 2017			128,782,878
Total stockholders' equity at Dec. 31, 2017		4,977,598	$ 1,305		4,287,487	723,471	(65,836)	31,171
Total stockholders' equity at Dec. 31, 2020		$ 3,594,951	$ 1,207		3,100,633	409,391	(88,803)	172,523
Shares, Outstanding at Dec. 31, 2020			118,414,853
Dividends declared per share (usd per share)		$ 2.40
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	[2]	$ 938
Shares, Outstanding at Dec. 31, 2018			123,189,833
Total stockholders' equity at Dec. 31, 2018		4,825,588	$ 1,251		3,722,723	1,182,674	(74,985)	(6,075)
Net Income		468,636				468,636
Other comprehensive income		84,733						84,733
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			798,248
net of shares forfeited		26,815	$ 8		26,807
Restricted stock surrendered, shares			(218,531)	3,987,945
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		40
Stock Repurchase Program		(8,449)					(8,449)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		154,516			154,476
Common stock, $1.35/share		(289,048)			(289,048)
Total stockholders' equity at Dec. 31, 2019		$ 4,954,697	$ 1,219		3,306,006	1,652,248	(83,434)	78,658
Shares, Outstanding at Dec. 31, 2019			119,781,605
New Accounting Pronouncement Or Change In Accounting Principle Effect Of Change of Income Taxes	[2]					938
Dividends declared per share (usd per share)		$ 2.30
Net Income		$ (1,237,574)				(1,237,574)
Other comprehensive income		93,865						93,865
Restricted stock awarded and earned stock compensation, net of shares forfeited, shares			800,537
net of shares forfeited		24,363	$ 8		24,355
Restricted stock surrendered, shares			(213,578)	1,953,711
Stock Repurchase Program, Number of Shares Authorized to be Repurchased		20
Stock Repurchase Program		(5,369)					(5,369)
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		70,000			69,980
Common stock, $1.35/share		(159,748)			(159,748)
Total stockholders' equity at Dec. 31, 2020		3,594,951	$ 1,207		$ 3,100,633	409,391	$ (88,803)	$ 172,523
Shares, Outstanding at Dec. 31, 2020			118,414,853
New Accounting Pronouncement Or Change In Accounting Principle Effect Of Change of Income Taxes	[3]	$ (5,283)				$ (5,283)

[1] Impact due to adoption on January 1, 2018 of ASU 2016-01, "Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities" and ASU 2018-02, "Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income."

[2] Impact due to adoption on January 1, 2019 of ASU 2016-02, "Leases (Topic 842)," and the related amendments.

[3] Impact due to adoption on January 1, 2020 of ASU 2016-13, "Financial Instruments - Credit Losses (ASC 326): Measurement of Credit Losses on Financial Instruments," and the related amendments, commonly referred to as CECL.