Other Retirement Plans (Multi-Employer Pension Plans, Details Of Company Contributions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	$ 20.7	[1]	$ 22.6		$ 5.1
Number of multi-employer pension plans allocated	35		35		35
Pipeline Industry Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	6.1	[1]	10.3	[1]	1.7	[1]
Expiration Date of CBA	May 31, 2012
Central Pension Fund Of The International Union Of Operating Engineers And Participating Employers [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	4.4	[1]	4.9	[1]	1.3	[1]
Expiration Date of CBA	Jan. 31, 2014
Laborers-Employers Benefit Plan Collection Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions		[1],[2]		[1],[2]	1.0	[1],[2]
Expiration Date of CBA	Jan. 31, 2014	[2]
Operating Engineers Pension Trust Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	1.2	[1]	1.0	[1]
Expiration Date of CBA	Jan. 31, 2014
Central States, Southeast And Southwest Areas Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.9	[1],[3]	0.8	[1],[3]	0.1	[1],[3]
Expiration Date of CBA	Mar. 31, 2012	[3]
Laborers Pension Trust Fund For Northern Nevada [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.8	[1]	0.4	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
New England Electrical Workers Money Purchase Plan And Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.7	[1],[5]	0.5	[1],[5]	0.4	[1],[5]
Expiration Date of CBA	Feb. 29, 2012	[5]
Laborers Local Union No. 158 Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.7	[1]	0.4	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
Laborers National Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.5	[1]	0.2	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
Eighth District Electrical Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.5	[1]
Expiration Date of CBA	Feb. 29, 2012
International Union Of Operating Engineers Pension Fund Of Eastern Pennsylvania And Delaware [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.5	[1]	0.3	[1]
Expiration Date of CBA	Jan. 31, 2014
Western Conference Of Teamsters Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.4	[1]	0.3	[1]
Expiration Date of CBA	Mar. 31, 2012
West Virginia Laborers Pension Trust Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.4	[1]	0	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
International Union Of Operating Engineers Local 132 Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.3	[1]	0	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
Minnesota Laborers Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.3	[1]	1.0	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
National Electrical Annuity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.3	[1],[5]	0.4	[1],[5]	0	[1],[5]
Expiration Date of CBA	May 31, 2012	[5]
International Brotherhood Of Electrical Workers Local 1249 Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.3	[1]			0	[1]
Expiration Date of CBA	May 05, 2013
Laborers District Council Of West Pennsylvania Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	0.3	[1]	0.2	[1]		[1],[4]
Expiration Date of CBA	Jan. 31, 2014
Other Multi-Employer Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Company Contributions	$ 2.1	[1]	$ 1.9	[1]	$ 0.6	[1]

[1] For the plans listed above, the Company is not aware of any current surcharge payments.

[2] Represents a trust to which one of the Company's subsidiaries makes contributions on behalf of several multi-employer pension plans. The trust allocates the subsidiary's contributions to the appropriate plans, of which there were approximately 35 for each of the three years ended December 31, 2011. Details of 2009's contributions by plan were not available as of December 31, 2011. Contributions to multi-employer pension plans made by this trust on our behalf for each of the two years in the period ended December 31, 2011 are reflected by plan in the table above.

[3] The Company's subsidiary that participated in the Central States, Southeast and Southwest Areas Pension Plan voluntarily withdrew from this plan in November 2011. See additional discussion below and in Note 16 - Commitment and Contingencies.

[4] Not available as of December 31, 2011. See (a) above.

[5] These plans are defined contribution multi-employer pension plans; therefore, PPA zone status disclosures in table below are not applicable.