Employee Benefits (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Maximum employee contribution as a percentage of annual compensation	100.00%
Matching percentage by company of first 4% of employee contribution	100.00%
Percentage of employee contribution fully matched by company	4.00%
Length of service required to be eligible for annual retirement contributions (in years)	1 year
Number of subsidiaries company provides post-retirement healthcare benefits to	2
Expected return on plan assets	7.00%
Percentage of investments for long-term growth included in investment strategy	65.00%
Percentage of investments for short-term growth included in investment strategy	35.00%
Discretionary range for pension fund trustee included in investment policy	10.00%
Matching Of Employee Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution savings plan expense	$ 5,180	$ 4,801	$ 4,556
Annual Retirement Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution savings plan expense	6,310	5,234	5,209
Salaried Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected 2011 contributions	1,164
Wage Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected 2011 contributions	930
Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated prior service cost to be amortized from other comprehensive income into net periodic benefit cost during 2012	297
Estimated net loss to be amortized from other comprehensive income into net periodic benefit cost during 2012	1,716
Post-Retirement Healthcare Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated prior service cost to be amortized from other comprehensive income into net periodic benefit cost during 2012	84
Estimated net loss to be amortized from other comprehensive income into net periodic benefit cost during 2012	$ 359
Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status of pension plans	80.00%
Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status of pension plans	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fixed income, target allocation percentage	55.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Fixed income, target allocation percentage	45.00%