Supplemental Compensation Plans, Assumptions Used to Determine Benefit Obligations (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Salary Continuation Plan [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate used to determine net periodic benefit cost for years ended	3.50%	4.30%	3.20%
Discount rate used to determine benefit obligations	3.80%	3.50%	4.30%
Future salary increases	4.00%	4.00%	4.00%
Directors' Retirement Plan [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate used to determine net periodic benefit cost for years ended	3.20%	4.10%	3.20%
Discount rate used to determine benefit obligations	3.40%	4.00%	4.10%