Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Future minimum lease payments to be received under noncancelable leases
2013	112,961
2014	91,528
2015	66,263
2016	50,527
2017	33,477
Thereafter	68,157
Total	422,913
Total operating revenues \| Customer concentration \| Customer one
Leases
Operating revenues (as a percent)	8.40%	11.40%	16.40%

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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