Savings and Retirement Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Maximum annual contribution per employee	$ 18,000	$ 17,500	$ 17,500
Employer match as a percent	50.00%	50.00%	50.00%
Employer contribution expense	$ 504,000	$ 442,000	$ 384,000
Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Liability to participants	$ 9,700,000	$ 10,300,000
Maximum | Pension Plan
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Maximum of employer match as a percentage of employee eligible earnings	5.00%	5.00%	5.00%