Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Federal: [Abstract]
Current	$ 28,362,000	$ 37,293,000	$ 28,140,000
Deferred	8,386,000	(1,417,000)	7,432,000
State and local: [Abstract]
Current	4,855,000	4,995,000	3,633,000
Deferred	118,000	(104,000)	121,000
Total	41,721,000	40,767,000	39,326,000
Effective income tax rate reconciliation [Abstract]
Statutory Federal income tax rate (in hundredths)	35.00%	35.00%	35.00%
State income tax, net of Federal benefit (in hundredths)	2.30%	2.60%	2.20%
Other (in hundredths)	(1.70%)	(0.70%)	(1.20%)
Effective Income Tax Rate, Continuing Operations, Total	35.60%	36.90%	36.00%
Deferred tax assets: [Abstract]
Stock compensation expense	307,000	1,620,000
Deferred compensation	848,000	2,193,000
Intangible asset amortization	145,000	229,000
Capital lease obligation	768,000	718,000
Other	143,000	221,000
Total deferred tax assets	2,211,000	4,981,000
Deferred tax liabilities: [Abstract]
Investments in securities available for sale	(7,408,000)	(5,166,000)
Investments In securities and partnerships	(12,502,000)	(6,213,000)
Contingent deferred sales commissions	(496,000)	(1,050,000)
Total deferred tax liabilities	(20,406,000)	(12,429,000)
Net deferred tax assets (liabilities)	(18,195,000)	(7,448,000)
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits [Roll Forward]
Balance beginning of the period	9,100,000	8,800,000	7,900,000
Additions based on tax positions related to the current year	1,100,000	700,000	1,400,000
Additions for tax positions of prior years	500,000	0	0
Reductions for tax positions of prior years	0	(400,000)	(400,000)
Settlements	(100,000)	0	(100,000)
Balance end of the period	10,600,000	9,100,000	8,800,000
Recognition of unrecognized tax benefits effect	7,000,000	6,000,000
Net liability for unrecognized tax benefits	9,900,000	8,300,000
Penalties and interest accruals related to tax uncertainties in income taxes	4,300,000	3,400,000
Income tax expenses related to an increase in its liability for interest and penalties	600,000	600,000	100,000
Reduction of Deferred tax asset from RSA acceleration			1,900,000
Increase to Additional Paid in Capital from RSA acceleration	$ 108,000