Condensed Consolidated Statement of Shareholders' Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance, December 31, 2016 at Dec. 31, 2016		$ 4,479,055	$ 1,228	$ 4,162,132	$ 366,073	$ (56,360)	$ 5,982
Shares outstanding, beginning balance (shares) at Dec. 31, 2016			121,283,669
Stockholders' Equity Disclosure [Rollforward]
Cumulative effect of change in accounting principle	[1]	291		711	(420)
Net earnings		273,781			273,781
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		27,631					27,631
Restricted stock awarded and earned compensation, net of shares forfeited (shares)			319,863
Restricted stock awarded and earned stock compensation, net of shares forfeited		20,198	$ 3	20,195
Restricted stock surrendered (shares)			(153,738)
Restricted stock surrendered		(7,793)				(7,793)
Cash dividends paid		(182,495)		(182,495)
Balance, September 30, 2017 at Sep. 30, 2017		$ 4,610,668	$ 1,231	$ 4,000,543	$ 639,434	$ (64,153)	$ 33,613
Shares outstanding, ending balance (shares) at Sep. 30, 2017			121,449,794

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