Comprehensive Income (Loss) (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassifications out of accumulated other comprehensive income
Cost of services rendered and products sold	$ (534,805)	$ (514,649)	$ (1,459,288)	$ (1,434,191)
Interest expense	(63,336)	(62,257)	(187,034)	(186,771)
Interest and net investment income	(2,360)	(3,961)	(6,528)	(7,999)
Provision (Benefit) for income taxes	(12,572)	94,303	118,110	95,956
Total reclassifications for the period	(45,688)	704,362	487,653	711,420
Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income
Total reclassifications for the period			1,241	13,091
(Gain) losses on derivatives | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income
Total before tax			3,118	17,893
Provision (Benefit) for income taxes			1,170	6,321
Total reclassifications for the period			1,948	11,572
(Gain) losses on derivatives | Amount Reclassified from Accumulated Other Comprehensive Income | Fuel swap contracts
Reclassifications out of accumulated other comprehensive income
Cost of services rendered and products sold			(1,613)	(1,718)
(Gain) losses on derivatives | Amount Reclassified from Accumulated Other Comprehensive Income | Interest rate swap contracts
Reclassifications out of accumulated other comprehensive income
Interest expense			4,731	19,611
(Gains) losses on available-for-sale securities | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income
Interest and net investment income			(1,160)	2,411
Provision (Benefit) for income taxes			(453)	892
Total reclassifications for the period			$ (707)	$ 1,519