Consolidated Statements of Changes in Stockholders' Equity Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Dividends on preferred stock (in dollars per share)	$ 398	$ 424	$ 850
Dividends on common stock (in dollars per share)	$ 0.55	$ 0.46	$ 0.42
Issuance of common shares pursuant to the Dividend Reinvestment Plan (in shares)	61,308	46,920	53,944
Issuance of common shares pursuant to the Deferred Compensation Plan (in shares)	13,724	12,700	6,048
Issuance of common shares pursuant to the First Retirement & Savings Plan (in shares)	8,971	9,747	19,366
Issuance of restricted common shares pursuant to the 2007 Stock Incentive Plan (in shares)	8,789	6,322	5,320
Stock Issued During Period, Shares, Conversion of Convertible Securities	1,139,426	0	0
number of preferred shares converted to common shares [Line Items]	4,927	0	0
Purchase of treasury shares (in shares)	86,681	202,170	165,117
Issuance of common shares pursuant to the exercise of stock options (in shares)	0	39,373	44,763
Treasury Stock, Shares, Retired	1,500,000	0	0
Preferred Stock
Stock Issued During Period, Shares, New Issues	0	0	1,650