Borrowings and Subordinated Debentures Borrowings and Subordinated Debentures (Details 1) $ in Thousands, € in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 555,146		$ 538,973
Debt Instrument, Unamortized Discount	(92,709)		(98,229)
Subordinated debentures	$ 462,437		440,744
Debt Instrument Date Issued	Jun. 30, 2006
Debt Instrument, Maturity Date	Sep. 18, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.85
Subordinated Debt Trust V Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.70%	4.70%	4.09%
Debt Instrument Date Issued	Aug. 15, 2003
Debt Instrument, Maturity Date	Sep. 17, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 3.10
Subordinated Debt Trust VI Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.64%	4.64%	4.01%
Debt Instrument Date Issued	Sep. 03, 2003
Debt Instrument, Maturity Date	Sep. 15, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 3.05
Subordinated Debt Trust CII Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 5,155		$ 5,155
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.55%	4.55%	3.95%
Debt Instrument Date Issued	Sep. 17, 2003
Debt Instrument, Maturity Date	Sep. 17, 2033
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.95
Subordinated Debt Trust VII Due April 2034 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 61,856		$ 61,856
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	4.13%	4.13%	3.64%
Debt Instrument Date Issued	Feb. 05, 2004
Debt Instrument, Maturity Date	Apr. 23, 2034
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.75
Subordinated Debt Trust CIII Due September 2035 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 20,619		$ 20,619
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.28%	3.28%	2.65%
Debt Instrument Date Issued	Aug. 15, 2005
Debt Instrument, Maturity Date	Sep. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.69
Subordinated Debt Trust FCCI Due March 2037 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 16,495		$ 16,495
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.19%	3.19%	2.56%
Debt Instrument Date Issued	Jan. 25, 2007
Debt Instrument, Maturity Date	Mar. 15, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.60
Subordinated Debt Trust FCBI Due December 2035 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 10,310		$ 10,310
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.14%	3.14%	2.51%
Debt Instrument Date Issued	Sep. 30, 2005
Debt Instrument, Maturity Date	Dec. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.55
Trust Preferred Securities Two Thousand Five Series One [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 82,475		$ 82,475
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.54%	3.54%	2.91%
Debt Instrument Date Issued	Nov. 21, 2005
Debt Instrument, Maturity Date	Dec. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Five Series Two [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 128,866		$ 128,866
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 14, 2005
Debt Instrument, Maturity Date	Jan. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Six One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 51,545		$ 51,545
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Feb. 22, 2006
Debt Instrument, Maturity Date	Apr. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Six Two Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 51,550		$ 51,550
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Sep. 27, 2006
Debt Instrument, Maturity Date	Oct. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Six Series Three [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 30,986		$ 27,185
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	1.72%	1.72%	1.74%
Debt Instrument Date Issued	Sep. 29, 2006
Debt Instrument, Maturity Date	Oct. 30, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month EURIBOR + 2.05
Liability, Reporting Currency Denominated, Value | €		€ 25.8
Trust Preferred Securities Two Thousand Six Series Four [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 16,470		$ 16,470
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 05, 2006
Debt Instrument, Maturity Date	Jan. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Trust Preferred Securities Two Thousand Six Series Five [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 6,650		$ 6,650
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Dec. 19, 2006
Debt Instrument, Maturity Date	Jan. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Two Thousand Seven One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 39,177		$ 39,177
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.33%	3.33%	2.84%
Debt Instrument Date Issued	Jun. 13, 2007
Debt Instrument, Maturity Date	Jul. 30, 2037
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.95
Subordinated Debentures Trust I Due March 2035 [Domain]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 6,186		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
Debt Instrument Date Issued	Dec. 10, 2004
Debt Instrument, Maturity Date	Mar. 15, 2035
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 2.05
Subordinated Debentures Trust II Due March 2036 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 3,093		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
Debt Instrument Date Issued	Dec. 23, 2005
Debt Instrument, Maturity Date	Mar. 15, 2036
Debt Instrument, Basis Spread on Variable Rate	3 month LIBOR + 1.75
Subordinated Debentures Trust III Due September 2036 [Member]
Subordinated Borrowing [Line Items]
Long-term Debt, Gross	$ 3,093		$ 0
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate			0.00%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust V Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.10%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust VI Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	3.05%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust CII Due September 2033 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.95%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust VII Due April 2034 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.75%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust CIII Due September 2035 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.69%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust FCCI Due March 2037 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.60%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debt Trust FCBI Due December 2035 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.55%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Five Series One [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Five Series Two [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Six One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Six Two Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Six Series Four [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Trust Preferred Securities Two Thousand Six Series Five [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Two Thousand Seven One Term Debt Securitization [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.95%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust I Due March 2035 [Domain]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.05%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.64%	3.64%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust II Due March 2036 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.34%	3.34%
London Interbank Offered Rate (LIBOR) [Member] | Subordinated Debentures Trust III Due September 2036 [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.85%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate	3.44%	3.44%
Euribor Rate [Member] | Trust Preferred Securities Two Thousand Six Series Three [Member]
Subordinated Borrowing [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.05%