Fair Value Measurements (Details 4) (USD $) In Thousands, unless otherwise specified							3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Recurring Level 3	Dec. 31, 2013 Recurring Level 3	Mar. 31, 2014 Recurring Level 3 Discounted cash flows Direct placement municipal securities	Dec. 31, 2013 Recurring Level 3 Discounted cash flows Direct placement municipal securities	Mar. 31, 2014 Recurring Level 3 Discounted cash flows Direct placement municipal securities Minimum	Dec. 31, 2012 Recurring Level 3 Discounted cash flows Direct placement municipal securities Minimum	Mar. 31, 2014 Recurring Level 3 Discounted cash flows Direct placement municipal securities Maximum	Dec. 31, 2012 Recurring Level 3 Discounted cash flows Direct placement municipal securities Maximum	Mar. 31, 2014 Non-recurring Level 3 Commercial loans	Mar. 31, 2014 Non-recurring Level 3 Minimum Commercial loans	Mar. 31, 2014 Non-recurring Level 3 Maximum Commercial loans	Mar. 31, 2014 Non-recurring Level 3 Auction values Autos	Mar. 31, 2014 Non-recurring Level 3 Trade publications and auction values Medium and heavy duty trucks	Mar. 31, 2014 Non-recurring Level 3 Trade publications and auction values Construction and environmental equipment	Mar. 31, 2014 Non-recurring Level 3 Appraisals Minimum Real estate	Mar. 31, 2014 Non-recurring Level 3 Trade publications Aircraft
Valuation methodology
Investment securities, available-for-sale	$ 839,597	$ 832,700	$ 4,709	$ 5,498	$ 4,709	$ 5,498
Unobservable Inputs
Credit spread assumption (as a percent)							0.89%	0.90%	1.52%	1.52%
Discount rate (as a percent)												40.00%	75.00%	10.00%	15.00%	20.00%	20.00%	10.00%
Discount rate (as a percent)											20.00%