Income Taxes (Reconciliation of Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Income tax expense at federal statutory rate									$ 89,677	$ 86,927	$ 72,567
Income tax expense (benefit) at federal statutory rate, Percent									35.00%	35.00%	35.00%
State and local income taxes, net of federal benefit									2,802	1,470	1,157
State and local income taxes, net of federal benefit, Percent									1.10%	0.60%	0.60%
Tax-exempt interest income, net									(8,517)	(9,577)	(10,052)
Tax-exempt interest income, net, Percent									(3.30%)	(3.80%)	(4.80%)
Increase in cash surrender value of life insurance									(4,819)	(3,939)	(3,626)
Increase in cash surrender value of life insurance, Percent									(1.90%)	(1.60%)	(1.70%)
Decrease in valuation allowance applicable to capital losses									(377)	(494)	(1,163)
(Decrease) increase in valuation allowance applicable to capital losses, Percent									(0.20%)	(0.20%)	(0.60%)
Other, net									(2,096)	278	(932)
Other, net, Percent									(0.80%)	0.10%	(0.50%)
Reported income tax expense	$ 18,755	$ 18,158	$ 20,835	$ 18,922	$ 20,261	$ 19,489	$ 18,312	$ 16,603	$ 76,670	$ 74,665	$ 57,951
Effective tax rate									29.90%	30.10%	28.00%