Acquisitions And Divestitures (Pro Forma Table Thompson and Bakken) (Details 3) (Bakken and Thompson Transactions [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Bakken and Thompson Transactions [Member]
Proforma revenue and net income
Pro forma total revenues and other income	$ 2,203,703	$ 2,184,507
Pro forma net income	$ 454,549	$ 523,227
Pro forma net income per common share:
Basic	$ 1.18	$ 1.32
Diluted	$ 1.17	$ 1.30