Deferred Compensation Benefits - Text (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Compensation Text Details [Line Items]
Amounts not recognized as net periodic benefit, net of tax	$ (9,782,000)	$ (5,168,000)	$ (6,426,000)
Pension loss (benefit) adjustment, net of tax	4,614,000	(1,258,000)	2,820,000
ESBP
Deferred Compensation Text Details [Line Items]
Net periodic pension cost	414,000	434,000	617,000
Benefit obligation	8,274,000	7,499,000	8,405,000
Comprehensive pension gain (loss), net of tax	(700,000)	400,000
Discount rate	3.30%	3.87%
Change in discount rate	(0.57%)
Increase (decrease) in plan liabilities	400,000
Estimated future employer contributions, next year	700,000
Employer contributions	737,000	720,000
Amounts not recognized as net periodic benefit, net of tax	2,000,000	1,300,000
Non Employee Director Deferred Compensation Plan [Member]
Deferred Compensation Text Details [Line Items]
Employer contributions	400,000	100,000	100,000
NDBP
Deferred Compensation Text Details [Line Items]
Net periodic pension cost	90,000	49,000	118,000
Benefit obligation	14,932,000	11,635,000	11,913,000
Discount rate	1.50%	3.20%
Change in discount rate	(1.70%)
Increase (decrease) in plan liabilities	4,400,000
Employer contributions	0	0
Targeted minimum return	4.00%	4.00%
Guaranteed rate of return	4.00%	4.00%
Amounts not recognized as net periodic benefit, net of tax	7,800,000	3,900,000
Key Employee Non Qualified Deferred Compensation Plan
Deferred Compensation Text Details [Line Items]
Estimated future employer contributions, next year	100,000
Employer contributions	200,000	300,000	400,000
ESBP and NDBP [Member]
Deferred Compensation Text Details [Line Items]
Pension loss (benefit) adjustment, net of tax	(5,100,000)	800,000	2,100,000
Amount to be recognized as components of net periodic benefit in next year	$ 400,000