Deferred Compensation Benefits - Textual (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Contributed defined benefit plan	4.00%	4.00%
Participants of plan	4.00%	4.00%
Amounts not recognized as net periodic benefit, net of tax	$ (6,426,000)	$ (3,606,000)	$ (1,863,000)
Amounts recognized as net periodic benefit, net of tax	2,820,000	1,743,000	542,000
Defined-contribution plan	100,000	100,000	100,000
NDBP
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Net periodic pension cost (benefit)	(118,000)	(77,000)	5,000
Accumulated benefit obligation	11,900,000	7,900,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	2.80%	4.60%
Discount rate decrease	1.80%
Pension and Other Postretirement Defined Benefit Plans, Increase in Plan's Liabilities	3,700,000
Amounts not recognized as net periodic benefit, net of tax	4,800,000	1,200,000
Defined Contribution Plan, Estimated Future Employer Contributions in Next Fiscal Year	0	42,000
ESBP
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Net periodic pension cost (benefit)	617,000	616,000	617,000
Accumulated benefit obligation	8,400,000	9,500,000
Other comprehensive income (loss), pension, net gain (loss) recognized, net of tax	600,000	400,000
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.02%	3.71%
Discount rate decrease	0.69%
Increase (decrease) in plan liabilities	400,000
Estimated future employer contributions, next year	700,000
Amounts not recognized as net periodic benefit, net of tax	1,700,000	2,300,000
Defined Contribution Plan, Estimated Future Employer Contributions in Next Fiscal Year	727,000	793,000
NDBP and ESPB
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Amounts recognized as net periodic benefit, net of tax	(2,100,000)	(1,100,000)	100,000
Amount to be reconized as compontents of net periodic benefit in next year	300,000
Key Employee Non Qualified Deferred Compensation Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Defined-contribution plan	400,000	300,000	100,000
Defined Contribution Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 300,000