Condensed Consolidated Statement of Shareholders' Equity - 6 months ended Jun. 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		172,315			172,315
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		23,747					23,747
Restricted stock awarded and earned compensation, net of shares forfeited (shares)			313,498
Restricted stock awarded and earned stock compensation, net of shares forfeited		13,719	$ 3	13,716
Restricted stock surrendered (shares)			(148,846)
Restricted stock surrendered		(7,558)				(7,558)
Cash dividends paid		(121,664)		(121,664)
Balance, June 30, 2017 at Jun. 30, 2017		$ 4,559,905	$ 1,231	$ 4,054,895	$ 537,968	$ (63,918)	$ 29,729
Shares outstanding, ending balance (shares) at Jun. 30, 2017			121,448,321

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