Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other assets — other notes and accounts receivable
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 1,043	$ 17	$ 0
Additions (Reductions) Charged to Costs and Expenses	346	1,039	17
Charged to Other Accounts	0	0	0
Deductions	614	13	0
Balance at End of Year	775	1,043	17
Current assets — supplies and inventory
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	12,589	13,107	12,701
Additions (Reductions) Charged to Costs and Expenses	503	1,961	1,755
Charged to Other Accounts	(2,274)	0	0
Deductions	2,372	2,479	1,349
Balance at End of Year	8,446	12,589	13,107
Deferred income taxes
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	34,663	2,831	737
Additions (Reductions) Charged to Costs and Expenses	8,659	31,832	2,416
Charged to Other Accounts	0	0	0
Deductions	0	0	322
Balance at End of Year	$ 43,322	$ 34,663	$ 2,831