Employee Benefits (Fair Value Measurement Inputs) (Details) (Retirement Plans, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Cash and Cash Equivalents	Dec. 31, 2011 Cash and Cash Equivalents	Dec. 31, 2012 US Treasury Securities	Dec. 31, 2011 US Treasury Securities	Dec. 31, 2012 Investment Contracts	Dec. 31, 2011 Investment Contracts	Dec. 31, 2012 Common Stock	Dec. 31, 2011 Common Stock	Dec. 31, 2012 Mututal Funds - Fixed Income	Dec. 31, 2011 Mututal Funds - Fixed Income	Dec. 31, 2012 Mutual Funds - Equity	Dec. 31, 2011 Mutual Funds - Equity	Dec. 31, 2012 Limited Partnership Interest in Real Estate		Dec. 31, 2011 Limited Partnership Interest in Real Estate		Dec. 31, 2010 Limited Partnership Interest in Real Estate	Dec. 31, 2012 Fair Value, Inputs, Level 1	Dec. 31, 2011 Fair Value, Inputs, Level 1	Dec. 31, 2012 Fair Value, Inputs, Level 1 Cash and Cash Equivalents	Dec. 31, 2011 Fair Value, Inputs, Level 1 Cash and Cash Equivalents	Dec. 31, 2012 Fair Value, Inputs, Level 1 US Treasury Securities	Dec. 31, 2011 Fair Value, Inputs, Level 1 US Treasury Securities	Dec. 31, 2012 Fair Value, Inputs, Level 1 Investment Contracts	Dec. 31, 2011 Fair Value, Inputs, Level 1 Investment Contracts	Dec. 31, 2012 Fair Value, Inputs, Level 1 Common Stock	Dec. 31, 2011 Fair Value, Inputs, Level 1 Common Stock	Dec. 31, 2012 Fair Value, Inputs, Level 1 Mututal Funds - Fixed Income	Dec. 31, 2011 Fair Value, Inputs, Level 1 Mututal Funds - Fixed Income	Dec. 31, 2012 Fair Value, Inputs, Level 1 Mutual Funds - Equity	Dec. 31, 2011 Fair Value, Inputs, Level 1 Mutual Funds - Equity	Dec. 31, 2012 Fair Value, Inputs, Level 1 Limited Partnership Interest in Real Estate		Dec. 31, 2011 Fair Value, Inputs, Level 1 Limited Partnership Interest in Real Estate		Dec. 31, 2012 Fair Value, Inputs, Level 2	Dec. 31, 2011 Fair Value, Inputs, Level 2	Dec. 31, 2012 Fair Value, Inputs, Level 2 Cash and Cash Equivalents	Dec. 31, 2011 Fair Value, Inputs, Level 2 Cash and Cash Equivalents	Dec. 31, 2012 Fair Value, Inputs, Level 2 US Treasury Securities	Dec. 31, 2011 Fair Value, Inputs, Level 2 US Treasury Securities	Dec. 31, 2012 Fair Value, Inputs, Level 2 Investment Contracts	Dec. 31, 2011 Fair Value, Inputs, Level 2 Investment Contracts	Dec. 31, 2012 Fair Value, Inputs, Level 2 Common Stock	Dec. 31, 2011 Fair Value, Inputs, Level 2 Common Stock	Dec. 31, 2012 Fair Value, Inputs, Level 2 Mututal Funds - Fixed Income	Dec. 31, 2011 Fair Value, Inputs, Level 2 Mututal Funds - Fixed Income	Dec. 31, 2012 Fair Value, Inputs, Level 2 Mutual Funds - Equity	Dec. 31, 2011 Fair Value, Inputs, Level 2 Mutual Funds - Equity	Dec. 31, 2012 Fair Value, Inputs, Level 2 Limited Partnership Interest in Real Estate		Dec. 31, 2011 Fair Value, Inputs, Level 2 Limited Partnership Interest in Real Estate		Dec. 31, 2012 Fair Value, Inputs, Level 3	Dec. 31, 2011 Fair Value, Inputs, Level 3	Dec. 31, 2012 Fair Value, Inputs, Level 3 Cash and Cash Equivalents	Dec. 31, 2011 Fair Value, Inputs, Level 3 Cash and Cash Equivalents	Dec. 31, 2012 Fair Value, Inputs, Level 3 US Treasury Securities	Dec. 31, 2011 Fair Value, Inputs, Level 3 US Treasury Securities	Dec. 31, 2012 Fair Value, Inputs, Level 3 Investment Contracts	Dec. 31, 2011 Fair Value, Inputs, Level 3 Investment Contracts	Dec. 31, 2012 Fair Value, Inputs, Level 3 Common Stock	Dec. 31, 2011 Fair Value, Inputs, Level 3 Common Stock	Dec. 31, 2012 Fair Value, Inputs, Level 3 Mututal Funds - Fixed Income	Dec. 31, 2011 Fair Value, Inputs, Level 3 Mututal Funds - Fixed Income	Dec. 31, 2012 Fair Value, Inputs, Level 3 Mutual Funds - Equity	Dec. 31, 2011 Fair Value, Inputs, Level 3 Mutual Funds - Equity	Dec. 31, 2012 Fair Value, Inputs, Level 3 Limited Partnership Interest in Real Estate		Dec. 31, 2011 Fair Value, Inputs, Level 3 Limited Partnership Interest in Real Estate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets at end of year	$ 220,568,000	$ 191,369,000	$ 9,163,000	$ 6,708,000	$ 24,854,000	$ 24,178,000	$ 1,059,000	$ 608,000	$ 52,149,000	$ 70,893,000	$ 59,150,000	$ 53,598,000	$ 65,634,000	$ 26,873,000	$ 8,559,000	[1]	$ 8,511,000	[1]	$ 7,757,000	$ 210,950,000	$ 182,250,000	$ 9,163,000	$ 6,708,000	$ 24,854,000	$ 24,178,000	$ 0	$ 0	$ 52,149,000	$ 70,893,000	$ 59,150,000	$ 53,598,000	$ 65,634,000	$ 26,873,000	$ 0	[1]	$ 0	[1]	$ 1,059,000	$ 608,000	$ 0	$ 0	$ 0	$ 0	$ 1,059,000	$ 608,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	[1]	$ 0	[1]	$ 8,559,000	$ 8,511,000	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 8,559,000	[1]	$ 8,511,000	[1]
Restriction Period To Sell Partnership Interest Minimum	5 years
Restriction Period To Sell Partnership Interest Maximum	7 years
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issuances, Settlements	$ 0	$ 0

[1] This investment is a commercial real estate partnership that purchases land, develops limited infrastructure, and sells it for commercial development. The Company is restricted from selling its partnership interest during the life of the partnership which is generally 5-7 years. Return of investment is realized as land is sold. The fair value of the limited partnership interest in real estate is based on the net asset value of the partnership which reflects the appraised value of the land.