Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	10.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	35.00%
Defined Contribution Plan, Employee Supplemental Contribution	65.00%
Defined Contribution Plan, Cost Recognized	$ 3,300,000	$ 2,900,000	$ 2,800,000
Pension and Other Postretirement Benefit Expense	1,100,000	1,200,000	1,100,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	21,400,000	19,600,000
Employee stock purchase plan, shares	36,188	38,926
Employee Share Purchase Plan, Shares Available for Purchase	1,924,886
Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense	202,000	172,000	94,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$ 4,400,000	$ 4,300,000
Minimum
Defined Benefit Plan Disclosure [Line Items]
Employee Stock Purchase Plan, Eligible Employee Purchase Discount	0.00%
Maximum
Defined Benefit Plan Disclosure [Line Items]
Employee Stock Purchase Plan, Eligible Employee Purchase Discount	15.00%