Pension Plan and Employee Benefits, Unobservable Input Reconciliation (Details) (Pension Benefits [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	$ 310,197	$ 241,844
Preferred Stock [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	291	1,446
Common/collective trust fund [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	94,677	113,529
Real estate funds [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	16,349	14,568
Hedge fund-of-funds [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	2,892	3,271
Level 3 [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning of period	17,839	20,156
Realized gain (loss)	17	81
Unrealized gain (loss)	1,531	780
Purchases, issuances, and settlements, net	(146)	(3,178)
Transfer out	0	0
Fair value of plan assets, end of period	19,241	17,839
Level 3 [Member] | Preferred Stock [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	0	0
Level 3 [Member] | Common/collective trust fund [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, end of period	0	0
Level 3 [Member] | Real estate funds [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning of period	14,568	13,627
Realized gain (loss)	0	0
Unrealized gain (loss)	1,454	612
Purchases, issuances, and settlements, net	327	329
Transfer out	0	0
Fair value of plan assets, end of period	16,349	14,568
Level 3 [Member] | Hedge fund-of-funds [Member]
Fair value of plan assets [Roll Forward]
Fair value of plan assets, beginning of period	3,271	6,529
Realized gain (loss)	17	81
Unrealized gain (loss)	77	168
Purchases, issuances, and settlements, net	(473)	(3,507)
Transfer out	0	0
Fair value of plan assets, end of period	$ 2,892	$ 3,271