Employee Stock Benefit Plans (401(k) Plan Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Salary Plan	Dec. 31, 2012 Salary Plan First Portion	Dec. 31, 2012 Salary Plan Remaining Portion	Dec. 31, 2012 Hourly Plan	Dec. 31, 2012 Hourly Plan First Portion	Dec. 31, 2013 Scenario, Forecast Salary Plan
Schedule of Defined Contribution Plans Disclosures [Line Items]
Minimum annual contribution per participating employee, percent				1.00%			1.00%
Maximum annual contribution per employee, percent				50.00%			25.00%
Employer matching contribution, percent of match					100.00%	50.00%		50.00%	100.00%
Employer matching contribution, percent					1.00%	5.00%		6.00%	6.00%
Maximum annual employer matching contributions per employee, percent of employee gross pay				3.50%
Maximum annual employer matching contributions per employee				$ 8,750			$ 7,500
Annual limit on eligible earnings imposed by Internal Revenue Code	250,000
Total matching contribution to all Plans	$ 2,300,000	$ 2,400,000	$ 2,400,000