Retirement Plans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employer Contribution Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of specified salary amount matched by employer	50.00%
Percentage of employee salary eligible for matching	4.00%
Employer contributions	$ 1,391,000	$ 1,030,000	$ 904,000
Employer Contribution Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of specified salary amount matched by employer	50.00%
Percentage of employee salary eligible for matching	4.00%
Employer contributions	781,000	697,000	667,000
Certain Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employee salary eligible for matching	3.00%
Defined Benefit Plan, Union Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 396,000	$ 369,000	$ 370,000