Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Federal [Abstract]
Current	$ 47,699	$ 58,194	$ 45,333
Deferred	(1,441)	(2,876)	371
State and local [Abstract]
Current	5,359	6,595	7,255
Deferred	109	(179)	15
Total	$ 51,726	$ 61,734	$ 52,974
Effective income tax rate reconciliation [Abstract]
Statutory Federal income tax rate	35.00%	35.00%	35.00%
State income tax, net of Federal benefit	2.70%	2.50%	2.30%
Other	(0.50%)	(0.80%)	(0.30%)
Effective income tax rate	37.20%	36.70%	37.00%
Deferred tax assets [Abstract]
Stock compensation expense	$ 4,857	$ 3,542
Deferred compensation	1,268	1,852
Deferred gain on asset sale	0	2,000
Capital lease obligation	905	859
Other	287	0
Total deferred tax assets	7,317	8,253
Deferred tax liabilities [Abstract]
Investments in securities available for sale	(5,443)	(9,362)
Contingent deferred sales commissions	(419)	(780)
Intangible asset amortization	(111)	0
Other	0	(25)
Total deferred tax liabilities	(5,973)	(10,167)
Net deferred tax assets	1,344
Net deferred tax (liabilities)		(1,914)
Increase (decrease) to additional paid in capital from RSA acceleration	(1,190)
Income tax uncertainties [Abstract]
Recognition of unrecognized tax benefits effect	11,900	10,400
Net liability for unrecognized tax benefits	17,600	15,000
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits [Roll Forward]
Balance, beginning of period	16,000	12,900	$ 10,600
Additions based on tax positions related to the current year	2,800	3,100	2,400
Additions for tax positions of prior years	100	0	500
Reductions for tax positions of prior years	(500)	0	(600)
Settlements	0	0	0
Balance, end of period	18,400	16,000	12,900
Penalties and interest accruals related to tax uncertainties in income taxes	8,000	6,700
Income tax expenses related to an increase in its liability for interest and penalties	$ 1,100	$ 1,000	$ 700
State Jurisdiction [Member] | New York [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Tax years under examination	2001
State Jurisdiction [Member] | New York [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Tax years under examination	2011