Income Taxes (Reconciliation of Provision (Benefit) for Income Taxes) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Income Taxes [Abstract]
Expected provision (benefit) at federal statutory rate	$ 416,632		$ (402,571)		$ 367,854
Increase (decrease) resulting from:
State income taxes, net of federal income tax effect	53,130		(44,454)		40,145
Nondeductible expenses	3,404		2,100		1,244
Other	13,708		1,786		3,978
Provision (benefit) for income taxes	$ 486,874	[1]	$ (443,139)	[1]	$ 413,221	[1]

[1] Interest expense and the provision (benefit) for income taxes by segment are an allocation of corporate amounts as they are incurred at the corporate level.