Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
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	$ 3,000,000	$ 3,000,000
Pension and Other Postretirement Benefit Expense	530,000	531,000	505,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities		8,000,000
Employee Stock Purchase Plan, Eligible Employee Purchase Discount	15.00%
Employee stock purchase plan, shares	38,926
Employee Share Purchase Plan, Shares Available for Purchase	1,961,074
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	172,000	94,000	132,000
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$ 4,000,000	$ 5,000,000
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%