Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands		Total		Common Stock	Additional Paid-in Capital	Retained Earnings		Treasury Stock	Shares Of Common Stock	Accumulated Other Comprehensive Income (Loss)
Dividends declared per share (usd per share)		$ 0.60
Beginning Period Balance at Dec. 31, 2018		$ 4,825,588		$ 1,251	$ 3,722,723	$ 1,182,674		$ (74,985)		$ (6,075)
Shares outstanding, beginning balance (shares) at Dec. 31, 2018				123,189,833
Stockholders' Equity Disclosure [Rollforward]
Net earnings		112,604				112,604
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		43,333								43,333
Restricted stock awarded and earned compensation, net of shares forfeited (shares)				195,536
Restricted stock awarded and earned stock compensation, net of shares forfeited		5,808		$ 2	5,806
Restricted stock surrendered (shares)				(113,544)					(3,070,676)
Restricted stock surrendered		(4,522)						(4,522)
Common stock repurchased under Stock Repurchase Program		(31)
Common stock repurchased under Stock Repurchase Program		(119,587)			(119,556)
Cash dividends paid		(73,180)			(73,180)
Ending Period Balance at Mar. 31, 2019		4,790,982		$ 1,222	3,535,793	1,296,216		(79,507)		37,258
Shares outstanding, ending balance (shares) at Mar. 31, 2019				120,201,149
Stockholders' Equity Disclosure [Rollforward]
New Accounting Pronouncement, Effect of Change on Net Income		938	[1]			938	[1]			0
Beginning Period Balance at Dec. 31, 2018		4,825,588		$ 1,251	3,722,723	1,182,674		(74,985)		(6,075)
Shares outstanding, beginning balance (shares) at Dec. 31, 2018				123,189,833
Stockholders' Equity Disclosure [Rollforward]
Net earnings		240,729
Ending Period Balance at Jun. 30, 2019		$ 4,852,010		$ 1,219	3,435,679	1,424,341		(82,295)		73,066
Shares outstanding, ending balance (shares) at Jun. 30, 2019				119,829,104
Dividends declared per share (usd per share)		$ 0.60
Beginning Period Balance at Mar. 31, 2019		$ 4,790,982		$ 1,222	3,535,793	1,296,216		(79,507)		37,258
Shares outstanding, beginning balance (shares) at Mar. 31, 2019				120,201,149
Stockholders' Equity Disclosure [Rollforward]
Net earnings		128,125				128,125
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		35,808								35,808
Restricted stock awarded and earned compensation, net of shares forfeited (shares)				619,653
Restricted stock awarded and earned stock compensation, net of shares forfeited		6,721		$ 6	6,715
Restricted stock surrendered (shares)				(74,429)					(917,269)
Restricted stock surrendered		(2,788)						(2,788)
Common stock repurchased under Stock Repurchase Program		(9)
Common stock repurchased under Stock Repurchase Program		(34,929)			(34,920)
Cash dividends paid		(71,909)			(71,909)
Ending Period Balance at Jun. 30, 2019		$ 4,852,010		$ 1,219	3,435,679	1,424,341		(82,295)		73,066
Shares outstanding, ending balance (shares) at Jun. 30, 2019				119,829,104
Dividends declared per share (usd per share)		$ 0.60
Beginning Period Balance at Dec. 31, 2019		$ 4,954,697		$ 1,219	3,306,006	1,652,248		(83,434)		78,658
Shares outstanding, beginning balance (shares) at Dec. 31, 2019				119,781,605
Stockholders' Equity Disclosure [Rollforward]
Net earnings		(1,433,111)				(1,433,111)
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		12,258								12,258
Restricted stock awarded and earned compensation, net of shares forfeited (shares)				194,916
Restricted stock awarded and earned stock compensation, net of shares forfeited		6,494		$ 2	6,492
Restricted stock surrendered (shares)				(106,021)					(1,953,711)
Restricted stock surrendered		(3,460)						(3,460)
Common stock repurchased under Stock Repurchase Program		(20)
Common stock repurchased under Stock Repurchase Program		(70,000)			(69,980)
Cash dividends paid		(71,206)			(71,206)
Ending Period Balance at Mar. 31, 2020		3,390,389		$ 1,201	3,171,312	213,854		(86,894)		90,916
Shares outstanding, ending balance (shares) at Mar. 31, 2020				117,916,789
Stockholders' Equity Disclosure [Rollforward]
New Accounting Pronouncement, Effect of Change on Net Income	[2]	(5,283)				(5,283)
Beginning Period Balance at Dec. 31, 2019		4,954,697		$ 1,219	3,306,006	1,652,248		(83,434)		78,658
Shares outstanding, beginning balance (shares) at Dec. 31, 2019				119,781,605
Stockholders' Equity Disclosure [Rollforward]
Net earnings		(1,399,907)
Ending Period Balance at Jun. 30, 2020		$ 3,452,898		$ 1,207	3,148,090	247,058		(88,495)		145,038
Shares outstanding, ending balance (shares) at Jun. 30, 2020				118,374,603
Dividends declared per share (usd per share)		$ 0.25
Beginning Period Balance at Mar. 31, 2020		$ 3,390,389		$ 1,201	3,171,312	213,854		(86,894)		90,916
Shares outstanding, beginning balance (shares) at Mar. 31, 2020				117,916,789
Stockholders' Equity Disclosure [Rollforward]
Net earnings		33,204				33,204
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		54,122								54,122
Restricted stock awarded and earned compensation, net of shares forfeited (shares)				550,738
Restricted stock awarded and earned stock compensation, net of shares forfeited		6,289		$ 6	6,283
Restricted stock surrendered (shares)				(92,924)
Restricted stock surrendered		(1,601)						(1,601)
Cash dividends paid		(29,505)			(29,505)
Ending Period Balance at Jun. 30, 2020		$ 3,452,898		$ 1,207	$ 3,148,090	$ 247,058		$ (88,495)		$ 145,038
Shares outstanding, ending balance (shares) at Jun. 30, 2020				118,374,603

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

[2] 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.