Pension Plan and Postretirement Benefits Other Than Pension (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Level 3 Private equity	Dec. 31, 2012 Pension Benefits	Dec. 31, 2011 Pension Benefits	Dec. 31, 2010 Pension Benefits	Dec. 31, 2009 Pension Benefits	Dec. 31, 2012 Pension Benefits Equity securities: Domestic	Dec. 31, 2011 Pension Benefits Equity securities: Domestic	Dec. 31, 2012 Pension Benefits Equity securities: Foreign	Dec. 31, 2011 Pension Benefits Equity securities: Foreign	Dec. 31, 2012 Pension Benefits Fixed income securities: Mortgage-backed securities	Dec. 31, 2011 Pension Benefits Fixed income securities: Mortgage-backed securities	Dec. 31, 2012 Pension Benefits Private equity	Dec. 31, 2012 Pension Benefits Gold bullion	Dec. 31, 2011 Pension Benefits Gold bullion	Dec. 31, 2012 Pension Benefits Total investment securities	Dec. 31, 2011 Pension Benefits Total investment securities	Dec. 31, 2012 Pension Benefits Cash and other	Dec. 31, 2011 Pension Benefits Cash and other	Dec. 31, 2012 Pension Benefits Level 1 Equity securities: Domestic	Dec. 31, 2011 Pension Benefits Level 1 Equity securities: Domestic	Dec. 31, 2012 Pension Benefits Level 1 Equity securities: Foreign	Dec. 31, 2011 Pension Benefits Level 1 Equity securities: Foreign	Dec. 31, 2012 Pension Benefits Level 1 Gold bullion	Dec. 31, 2011 Pension Benefits Level 1 Gold bullion	Dec. 31, 2012 Pension Benefits Level 1 Total investment securities	Dec. 31, 2011 Pension Benefits Level 1 Total investment securities	Dec. 31, 2012 Pension Benefits Level 2 Fixed income securities: Mortgage-backed securities	Dec. 31, 2011 Pension Benefits Level 2 Fixed income securities: Mortgage-backed securities	Dec. 31, 2012 Pension Benefits Level 2 Total investment securities	Dec. 31, 2011 Pension Benefits Level 2 Total investment securities	Dec. 31, 2012 Pension Benefits Level 3 Private equity	Dec. 31, 2012 Pension Benefits Level 3 Total investment securities
Pension Plan and Postretirement Benefits Other than Pension
Total fair value	$ 1,772	$ 133,911	$ 103,404	$ 106,568	$ 91,551	$ 51,289	$ 44,818	$ 53,291	$ 38,942	$ 50	$ 98	$ 1,772	$ 13,452	$ 12,857	$ 119,854	$ 96,715	$ 14,057	$ 6,689	$ 51,289	$ 44,818	$ 53,291	$ 38,942	$ 13,452	$ 12,857	$ 118,032	$ 96,617	$ 50	$ 98	$ 50	$ 98	$ 1,772	$ 1,772
Summary of the activity of plan assets categorized as Level 3 during the period
Fair value of plan assets at beginning of year		133,911	103,404	106,568	91,551	51,289	44,818	53,291	38,942	50	98	1,772	13,452	12,857	119,854	96,715	14,057	6,689	51,289	44,818	53,291	38,942	13,452	12,857	118,032	96,617	50	98	50	98	1,772	1,772
Purchases, issuances and settlements	1,772
Fair value of plan assets at end of year	$ 1,772	$ 133,911	$ 103,404	$ 106,568	$ 91,551	$ 51,289	$ 44,818	$ 53,291	$ 38,942	$ 50	$ 98	$ 1,772	$ 13,452	$ 12,857	$ 119,854	$ 96,715	$ 14,057	$ 6,689	$ 51,289	$ 44,818	$ 53,291	$ 38,942	$ 13,452	$ 12,857	$ 118,032	$ 96,617	$ 50	$ 98	$ 50	$ 98	$ 1,772	$ 1,772