Equity Change in OCI Recognized in Statement of Operations, Line Item (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015	[1]	Mar. 31, 2015	[1]	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investments, net																	$ 521		$ 236		$ (7)
Interest Expense, Junior Subordinated Debentures																	2,427		3,875		3,872
Interest Expense, Deposits																	16,571		16,002		14,102
Income tax expense/(benefit)	$ 7,247		$ 8,652		$ 7,626		$ 7,438		$ 5,638		$ 8,182		$ 8,000		$ 8,572		30,963	[2]	30,392	[2]	32,365	[2]
Net income attributable to the Company	$ 17,552		$ 19,636		$ 16,398		$ 18,041		$ 15,002		$ 13,530		$ 17,610		$ 18,783		71,628		64,925		68,815
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax																	(979)		(2,354)		(1,849)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investments, net																	521		236		(7)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense/(benefit)																	190		97		(3)
Net income attributable to the Company																	331		139		(4)
Hedges related to junior subordinated debt [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense, Junior Subordinated Debentures																	0		1,879		1,926
Income tax expense/(benefit)																	0		804		824
Net income attributable to the Company																	0		(1,075)		(1,102)
Hedges related to deposits [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense, Deposits																	1,666		2,173		1,272
Income tax expense/(benefit)																	687		894		525
Net income attributable to the Company																	$ (979)		$ (1,279)		$ (747)

[1] Due to rounding, the sum of the four quarters may not add to the year to date total.

[2] The Company’s effective tax rate for 2016, 2015, and 2014 is not consistent due to earnings from tax-exempt investments, non-deductible compensation, state and local taxes, income tax credits and income attributable to noncontrolling interests having a different impact on the effective tax rate due primarily to the different levels of income before taxes in years 2016, 2015, and 2014. See Part II. Item 8. “Financial Statements and Supplementary Data - Note 17: Income Taxes” for additional details.