Pension and Other Postretirement Benefits (Details Textual)	12 Months Ended										12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended															12 Months Ended		12 Months Ended					12 Months Ended
	Dec. 31, 2012 USD ($) Employees	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2012 Multi-employer plan [Member] Employees	Dec. 31, 2012 U.S. Pension Benefits [Member] USD ($)		Dec. 31, 2011 U.S. Pension Benefits [Member] USD ($)		Dec. 31, 2010 U.S. Pension Benefits [Member] USD ($)		Dec. 31, 2012 U.S. Pension Benefits [Member] Equity Securities [Member] USD ($)	Dec. 31, 2011 U.S. Pension Benefits [Member] Equity Securities [Member] USD ($)	Dec. 31, 2012 U.S. Pension Benefits [Member] Other Investments [Member] USD ($)	Dec. 31, 2011 U.S. Pension Benefits [Member] Other Investments [Member] USD ($)	Dec. 31, 2012 U.S. Pension Benefits [Member] Fixed-Income Securities [Member] USD ($)	Dec. 31, 2011 U.S. Pension Benefits [Member] Fixed-Income Securities [Member] USD ($)	Dec. 31, 2012 U.S. Pension Benefits [Member] Cash and Cash Equivalents [Member] USD ($)	Dec. 31, 2011 U.S. Pension Benefits [Member] Cash and Cash Equivalents [Member] USD ($)	Dec. 31, 2012 U.S. Pension Benefits [Member] Managed Funds [Member] Equity Securities [Member]	Dec. 31, 2011 U.S. Pension Benefits [Member] Managed Funds [Member] Equity Securities [Member]	Dec. 31, 2012 U.S. Pension Benefits [Member] Managed Funds [Member] Other Investments [Member] USD ($)		Dec. 31, 2011 U.S. Pension Benefits [Member] Managed Funds [Member] Other Investments [Member] USD ($)		Dec. 31, 2012 U.S. Pension Benefits [Member] Managed Funds [Member] Fixed-Income Securities [Member]	Dec. 31, 2011 U.S. Pension Benefits [Member] Managed Funds [Member] Fixed-Income Securities [Member]	Dec. 31, 2012 U.S. Pension Benefits [Member] Managed Funds [Member] Cash and Cash Equivalents [Member]	Dec. 31, 2011 U.S. Pension Benefits [Member] Managed Funds [Member] Cash and Cash Equivalents [Member]	Dec. 31, 2012 U.K. pension benefits plan [Member] USD ($)	Dec. 31, 2011 U.K. pension benefits plan [Member] USD ($)	Dec. 31, 2010 U.K. pension benefits plan [Member] USD ($)	Dec. 31, 2012 U.K. pension benefits plan [Member] GBP (£)	Dec. 31, 2011 U.K. pension benefits plan [Member] GBP (£)	Dec. 31, 2012 U.K. pension benefits plan [Member] Equity Securities [Member] USD ($)	Dec. 31, 2011 U.K. pension benefits plan [Member] Equity Securities [Member] USD ($)	Dec. 31, 2012 U.K. pension benefits plan [Member] Other Investments [Member]	Dec. 31, 2012 U.K. pension benefits plan [Member] Fixed-Income Securities [Member]	Dec. 31, 2012 U.K. pension benefits plan [Member] Cash and Cash Equivalents [Member]	Dec. 31, 2012 Nonqualified defined benefit pension plan [Member] USD ($)	Dec. 31, 2011 Nonqualified defined benefit pension plan [Member] USD ($)	Dec. 31, 2012 Other Postretirement Benefits [Member] USD ($) Customers	Dec. 31, 2011 Other Postretirement Benefits [Member] USD ($)	Dec. 31, 2010 Other Postretirement Benefits [Member] USD ($)
Defined Benefit Plan Disclosure [Line Items]
Minimum contributions required					$ 0
Voluntary contributions made	0	7,000,000	5,000,000		36,000	[1]	7,045,000	[1]																					1,786,000	1,693,000	1,420,000										642,000	650,000
Minimum contributions expected in 2013																																							0
Estimated benefit payments, in 2013					8,334,000																								1,169,000										25,000		764,000
Estimated benefit payments, in 2014					8,815,000																								1,239,000										35,000		809,000
Estimated benefit payments, in 2015					9,267,000																								1,549,000										44,000		840,000
Estimated benefit payments, in 2016					9,699,000																								1,460,000										53,000		862,000
Estimated benefit payments, in 2017					10,149,000																								2,167,000										70,000		871,000
Estimated benefit payments, in 2018-2022					57,898,000																								12,660,000										1,860,000		5,068,000
Fair value of plan assets					140,218,000	[1]	133,403,000	[1]	135,730,000	[1]	77,080,000	71,987,000	36,554,000	35,220,000	20,921,000	20,776,000	5,663,000	5,420,000			30,064,000	[2]	29,280,000	[3]					41,875,000	36,436,000	34,836,000	25,774,000	23,443,000	18,417,000	16,932,000						0	0	0
Accumulated benefit obligations					180,737,000		161,126,000																						59,210,000	50,698,000		36,443,000	32,620,000						2,082,000	1,698,000
Employer contribution expected in 2013																													1,825,000
Contributions to defined contribution pension plan																													311,000	415,000	337,000
Contributions to the defined contribution pension plan expected in 2013																													375,000
Fair market value included in other noncurrent assets																																							3,358,000	3,090,000
Number of employers contributed to the plan				1,038
Number of employees participate in the plan	100,000
Multiemployer plan number of employees description	in excess of 100,000
Corporation's contributions	241,000	246,000	232,000
Percentage of employers contributions	5.00%
Contributions expected in 2013	275
Number of subsidiary having postretirement health care benefits																																									1
Service period to avail existing pension plan	15 years
Percentage of assets to invest in a diversified portfolio of fixed income securities of varying maturities	65.00%
Investments in diversified portfolio	Invests at least 65% of its assets in a diversified portfolio of fixed income securities of varying maturities
Target allocation	Generate a minimum annual inflation adjusted return of 5% and outperform a traditional 70/30 equities/bond portfolio.
Percentage of managed fund											65.00%		15.00%		15.00%		5.00%		57.00%	54.00%	32.00%		35.00%		10.00%	10.00%	1.00%	1.00%						44.00%		21.00%	35.00%	0.00%
High-quality fixed-income investments maturity	10 years
Percentage decrease in other postretirement benefits in 2013																																									4.75%
Percentage decrease in other postretirement benefits in 2017																																									2018
Percentage point increase or decrease in the assumed health care cost trend rate																																									1.00%
One percent effect on postretirement benefit obligation																																									3,400,000
Annual benefit expense																																									260,000
Pension and Other Postretirement Benefits (Textual) [Abstract]
Total amount of assets collected	$ 8,500,000,000
Percentage of funded status in excess	100.00%
Participation of corporation's employees in the plan	Less than 100
Percentage of projected benefit obligations to be amortized	10.00%
Percentage of projected benefit obligations included in net periodic pension and other postretirement costs	10.00%
Assumed health care cost trend rate	7.00%

[1] Includes the non-qualified defined benefit pension plan.

[2] Includes approximately 57% in equity and equity-like asset securities, 32% in alternative investments (real assets, commodities and resources, absolute return funds), 10% fixed income securities and 1% in cash and cash equivalents.

[3] Includes approximately 54% in equity and equity-like asset securities, 35% in alternative investments (real assets, commodities and resources, absolute return funds), 10% fixed income securities and 1% in cash and cash equivalents.