Condensed Consolidated Statement of Shareholders' Equity - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Total	Shares Of Common Stock	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	291			711	(420)
Net earnings	78,668				78,668
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax	6,736						6,736
Restricted stock awarded and earned compensation, net of shares forfeited (shares)		165,648
Restricted stock awarded and earned stock compensation, net of shares forfeited	6,470		$ 2	6,468
Restricted stock surrendered (shares)			(41,184)
Restricted stock surrendered	(2,281)					(2,281)
Cash dividends paid	(60,833)			(60,833)
Balance, March 31, 2017 at Mar. 31, 2017	$ 4,508,106		$ 1,230	$ 4,108,478	$ 444,321	$ (58,641)	$ 12,718
Shares outstanding, ending balance (shares) at Mar. 31, 2017		121,408,133