Employee Benefit Plans - Assumptions Used in Determining Retirement Plans Expense (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans [Member]
Assumptions used in determining annual retirement plan expense [Abstract]
Discount rate	3.46%	4.27%	3.33%
Long-term rate of return on plan assets	7.50%	7.50%	7.50%
Increase in compensation levels	4.54%	5.05%	5.37%
SERP [Member]
Assumptions used in determining annual retirement plan expense [Abstract]
Discount rate	3.14%	3.62%	2.76%
Increase in compensation levels	4.41%	4.83%	5.05%