Accounting Policies - Depreciation Life Study (Details Textual) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Change in Accounting Estimate [Line Items]
Change in depreciation expense	$ 52,877	$ 89,782	$ 228,833	$ 276,769
Increase in Net Income	(8,960)	(37,329)	(99,553)	(121,114)
Service Life
Change in Accounting Estimate [Line Items]
Change in depreciation expense	29,000
Increase in Net Income	$ 27,000
Earnings per share	$ 1.03