Segment Reporting (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue:
Revenue	$ 1,583,536	$ 1,573,295	$ 1,563,860	$ 1,536,276	$ 1,541,094	$ 1,570,720	$ 1,513,344	$ 1,425,376	$ 6,256,967	$ 6,050,534	$ 5,136,435
Long-lived assets
Total	6,379,461				5,673,851				6,379,461	5,673,851	4,808,061
United States [Member]
Revenue:
Revenue									5,231,899	5,075,432	4,313,483
Long-lived assets
Total	5,261,622				4,708,086				5,261,622	4,708,086	4,098,735
Foreign [Member]
Revenue:
Revenue									1,025,068	975,102	822,952
Long-lived assets
Total	1,117,839				965,765				1,117,839	965,765	709,326
Canada [Member]
Revenue:
Revenue									477,495	481,593	466,405
Long-lived assets
Total	557,351				481,139				557,351	481,139	468,062
Europe [Member]
Revenue:
Revenue									384,105	324,214	219,508
Long-lived assets
Total	534,728				463,848				534,728	463,848	219,178
Mexico [Member]
Revenue:
Revenue									143,282	147,464	122,312
Long-lived assets
Total	24,973				19,931				24,973	19,931	21,194
Asia [Member]
Revenue:
Revenue									20,186	21,831	14,727
Long-lived assets
Total	$ 787				$ 847				$ 787	$ 847	$ 892