Pension Plan and Employee Benefits, Fair Value of Pension Plan Assets (Details) (Pension Benefits [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 310,197	$ 241,844
Interest accrual	2,198	669
Total net assets	312,395	242,513	221,067
Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,775	6,512
Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15,242	29,651
Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	291	1,446
Obligations of U.S. Government and U.S. Government Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28,501	24,038
Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,144	12,294
Common/collective trust fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,677	113,529
Real estate funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,349	14,568
Hedge fund-of-funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,892	3,271
Corporate debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	135,326	36,535
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,144	12,294
Level 1 [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Obligations of U.S. Government and U.S. Government Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,144	12,294
Level 1 [Member] | Common/collective trust fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Real estate funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Hedge fund-of-funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 [Member] | Corporate debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	281,812	211,711
Level 2 [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,775	6,512
Level 2 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15,242	29,651
Level 2 [Member] | Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	291	1,446
Level 2 [Member] | Obligations of U.S. Government and U.S. Government Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28,501	24,038
Level 2 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Common/collective trust fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,677	113,529
Level 2 [Member] | Real estate funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Hedge fund-of-funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 [Member] | Corporate debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	135,326	36,535
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,241	17,839	20,156
Level 3 [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Common Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Obligations of U.S. Government and U.S. Government Agencies [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Common/collective trust fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 3 [Member] | Real estate funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,349	14,568	13,627
Level 3 [Member] | Hedge fund-of-funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,892	3,271	6,529
Level 3 [Member] | Corporate debt [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0