Investment in Securities, Part I (Details) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Available for sale securities:
Available-for-sale Securities, Cost	$ 79,665,000	$ 40,207,000	$ 38,178,000
Available for sale securities, Fair Value	120,202,000us-gaap_AvailableForSaleSecurities	85,407,000us-gaap_AvailableForSaleSecurities	79,846,000us-gaap_AvailableForSaleSecurities
Investments in securities	158,788,000us-gaap_MarketableSecurities	234,414,000us-gaap_MarketableSecurities	259,537,000us-gaap_MarketableSecurities
Amount Reclassified from AOCI [Abstract]
Net gain from investments - Realized gain / (loss) on sale of securities	25,000	1,612,000
Other operating expenses	0	3,141,000
Other Comprehensive Income (Loss), Reclassification Adjustment for Write-down of Securities Included in Net Income, before Tax	0	0
Income before income taxes	25,000	4,753,000
Income tax provision	(9,000)	(1,759,000)
Net income	16,000	2,994,000
Gross Amounts Not Offset in the Statements of Financial Position, Liabilities [Abstract]
Net gain/(loss) on equity derivative	131,000	(190,000)
Shares under derivative contract (in shares)	0.4	1.9	3.8
Derivative fair value of derivative net	88,000	(107,000)	262,000
Swaps [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	128,000	198,000	896,000
Gross amounts offset in the Statements of Financial Position	0	0	0
Net Amounts of Assets Presented in the Statements of Financial Position	128,000	198,000	896,000
Gross Amounts Not Offset in the Statements of Financial Position, Assets [Abstract]
Financial Instruments	(23,000)	(198,000)	(634,000)
Cash collateral received	0	0	0
Net amount	105,000	0	262,000
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	23,000	277,000	634,000
Gross amounts offset in the Statements of Financial Position	0	0	0
Net Amounts of Assets Presented in the Statements of Financial Position	23,000	277,000	634,000
Gross Amounts Not Offset in the Statements of Financial Position, Liabilities [Abstract]
Financial Instruments	(23,000)	(198,000)	(634,000)
Cash collateral received	0	0	0
Net amount	0	79,000	0
Investment in Securities [Member]
Trading securities:
Trading Securities, Cost	111,934,000	176,875,000	207,464,000
Trading securities, fair value	158,788,000	234,414,000	259,537,000
Investment in Securities [Member] \| Trading Securities [Member]
Trading securities:
Trading Securities, Cost	97,698,000	161,172,000	193,146,000
Trading securities, fair value	119,546,000	191,428,000	219,227,000
Trading Securities:
Cost	8,488,000	8,922,000	9,836,000
Fair Value	8,569,000	10,788,000	10,595,000
Investment in Securities [Member] \| Trading Securities [Member] \| Government obligations [Member]
Trading securities:
Trading Securities, Cost	9,998,000	25,989,000	18,994,000
Trading securities, fair value	9,998,000	25,999,000	18,996,000
Investment in Securities [Member] \| Trading Securities [Member] \| Common Stock [Member]
Trading securities:
Trading Securities, Cost	84,646,000	113,508,000	170,977,000
Trading securities, fair value	105,190,000	141,276,000	195,029,000
Trading Securities:
Cost	8,485,000	8,837,000	9,835,000
Fair Value	8,530,000	10,469,000	9,960,000
Investment in Securities [Member] \| Trading Securities [Member] \| Mutual Funds [Member]
Trading securities:
Trading Securities, Cost	2,505,000	21,131,000	2,432,000
Trading securities, fair value	3,596,000	23,404,000	3,498,000
Investment in Securities [Member] \| Trading Securities [Member] \| Other Investments [Member]
Trading securities:
Trading Securities, Cost	549,000	544,000	743,000
Trading securities, fair value	762,000	749,000	1,704,000
Trading Securities:
Cost	3,000	85,000	1,000
Fair Value	39,000	319,000	635,000
Investment in Securities [Member] \| Available-for-sale Securities [Member]
Trading securities:
Trading Securities, Cost	14,236,000	15,703,000	14,318,000
Trading securities, fair value	39,242,000	42,986,000	40,310,000
Investment in Securities [Member] \| Available-for-sale Securities [Member] \| Common Stock [Member]
Trading securities:
Trading Securities, Cost	13,609,000	15,003,000	13,637,000
Trading securities, fair value	37,954,000	41,538,000	38,942,000
Investment in Securities [Member] \| Available-for-sale Securities [Member] \| Mutual Funds [Member]
Trading securities:
Trading Securities, Cost	627,000	700,000	681,000
Trading securities, fair value	1,288,000	1,448,000	1,368,000
Investment in Sponsored Registered Investment Companies [Member]
Available for sale securities:
Available-for-sale Securities, Cost	102,526,000	24,523,000	23,861,000
Available for sale securities, Fair Value	120,831,000	42,433,000	39,537,000
Investment in Sponsored Registered Investment Companies [Member] \| Trading Securities [Member]
Available for sale securities:
Available-for-sale Securities, Cost	37,097,000	19,000	1,000
Available for sale securities, Fair Value	39,871,000	12,000	1,000
Investment in Sponsored Registered Investment Companies [Member] \| Trading Securities [Member] \| Mutual Funds [Member]
Available for sale securities:
Available-for-sale Securities, Cost	37,097,000	19,000	1,000
Available for sale securities, Fair Value	39,871,000	12,000	1,000
Investment in Sponsored Registered Investment Companies [Member] \| Available-for-sale Securities [Member]
Available for sale securities:
Available-for-sale Securities, Cost	65,429,000	24,504,000	23,860,000
Available for sale securities, Fair Value	80,960,000	42,421,000	39,536,000
Investment in Sponsored Registered Investment Companies [Member] \| Available-for-sale Securities [Member] \| Mutual Funds [Member]
Available for sale securities:
Available-for-sale Securities, Cost	1,891,000	1,939,000	1,898,000
Available for sale securities, Fair Value	3,297,000	3,441,000	3,213,000
Investment in Sponsored Registered Investment Companies [Member] \| Available-for-sale Securities [Member] \| Closed end Funds [Member]
Available for sale securities:
Available-for-sale Securities, Cost	63,538,000	22,565,000	21,962,000
Available for sale securities, Fair Value	$ 77,663,000	$ 38,980,000	$ 36,323,000

The total before tax amount of reclassifications from accumulated other comprehensive income (loss).

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