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)		$ 0.50
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]
Cumulative effect of change in accounting principle	[1]	938			938			0
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
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]
Cumulative effect of change in accounting principle	[1]	(5,283)			(5,283)
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

[1] 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.