Employee Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Retirement savings plan, contributions by employer	$ 948,000	$ 943,000	$ 956,000
Health insurance benefits cost	$ 1,200,000	$ 1,100,000	$ 1,100,000