Income Taxes (Schedule Of Company's Actual Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed “expected” tax expense	$ 150,461	$ 139,840	$ 133,112
Tax-exempt interest, net of cost to carry	(20,295)	(20,033)	(19,083)
Effective Income Tax Rate Reconciliation, Contribution of Appreciated Securities, Amount	(10,864)	0	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	(6,753)	0	0
Effective Income Tax Rate Reconciliation, Share-based Award Payments, Amount	(6,613)	0	0
State and local income taxes, net of federal tax benefit	5,955	6,132	4,484
Tax deductible dividends on allocated shares held by the Company’s ESOP	(966)	(1,044)	(1,093)
Other	(419)	(744)	(830)
Total income tax expense	$ 110,506	$ 124,151	$ 116,590