Employee Benefits Plans (Details 9) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 6,746	$ 5,988	$ 5,199
Western Conference Teamsters [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Number	91-6145047
Pension Protection Act Zone Status	Green	Green
FIP/RP Status Pending/ Implemented	No
Contributions	1,943	1,855	1,494
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	6/30/14 to 3/31/16
IAM National [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Number	51-6031295
Pension Protection Act Zone Status	Green	Green
FIP/RP Status Pending/ Implemented	No
Contributions	2,038	1,794	1,573
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	4/30/13 to 3/31/17
Automobile Mechanics Local No. 701 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Number	36-6042061
Pension Protection Act Zone Status	Red	Red
FIP/RP Status Pending/ Implemented	FIP Adopted
Contributions	1,527	1,203	1,076
Surcharge Imposed	Yes
Expiration Date of Collective Bargaining Agreement	5/31/13 to 10/31/14
International Association of Machinists Motor City [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Number	38-6237143
Pension Protection Act Zone Status	Red (2)	Red (2)
FIP/RP Status Pending/ Implemented	RP adopted
Contributions	437	392	372
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	1/31/14 to 3/31/16
Central States Southwest and Southwest Areas [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Plan Number	36-6044243
Pension Protection Act Zone Status	Red	Red
FIP/RP Status Pending/ Implemented	RP adopted
Contributions	226	182	158
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	6/1/12 to 5/31/17
Other Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 575	$ 562	$ 526