Condensed Consolidated Statement of Shareholders' Equity - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Shares Of Common Stock [Member]	Accumulated Other Comprehensive Income (Loss)
Balance, December 31, 2017 at Dec. 31, 2017		$ 4,977,598	$ 1,305	$ 4,287,487	$ 723,471	$ (65,836)		$ 31,171
Shares outstanding, beginning balance (shares) at Dec. 31, 2017			128,782,878
Stockholders' Equity Disclosure [Rollforward]
Cumulative effect of change in accounting principle	[1]	0		0	(6,136)
Net earnings		118,276			118,276
Other comprehensive income - net unrealized gain on securities available-for-sale, net of tax		(49,243)						(49,243)
Restricted stock awarded and earned compensation, net of shares forfeited (shares)			96,034
Restricted stock awarded and earned stock compensation, net of shares forfeited		7,199	$ 1	7,198
Restricted stock surrendered (shares)			(55,186)				(2,285,855)
Restricted stock surrendered		(2,858)				(2,858)
Cash dividends paid		(63,689)		(63,689)
Balance, March 31, 2018 at Mar. 31, 2018		$ 4,867,490	$ 1,283	4,111,226	$ 835,611	(68,694)		$ (11,936)
Shares outstanding, ending balance (shares) at Mar. 31, 2018			126,537,871
Stockholders' Equity Disclosure [Rollforward]
Stock Repurchased During Period, Shares		23,000
Common Stock Repurchased Under Stock Repurchase Program, Amount Repurchased		$ 119,793		$ 119,770		$ 0

[1] Impact due to adoption on January 1, 2018 of