Pension Plan and Employee Benefits, Pension Plan Asset Investment Objectives (Details)	12 Months Ended
	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Maximum notional value of derivative positions of the total pension fund's value	20.00%
Pension Benefits [Member] | Domestic Equity [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	21.00%
Pension Benefits [Member] | International Equity [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	18.00%
Pension Benefits [Member] | Real estate funds [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	8.00%
Pension Benefits [Member] | Hedge Funds [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	2.00%
Pension Benefits [Member] | Return Seeking [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations, minimum	43.00%
Target plan allocations	49.00%
Target plan allocations, maximum	53.00%
Pension Benefits [Member] | Fixed income- long government/credit [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	17.00%
Pension Benefits [Member] | Fixed income- long credit [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations	36.00%
Pension Benefits [Member] | Liability Hedging [Member]
Investment asset allocation target percentage of total plan assets [Abstract]
Target plan allocations, minimum	47.00%
Target plan allocations	53.00%
Target plan allocations, maximum	57.00%