Employee Benefits Plans (Details 9) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 8,554	$ 8,406	$ 6,746
Pension settlement charges	12,564	2,820	0
Union-administered plans	138,656	48,118	49,413
Union Administered Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Union-administered plans	21,118	11,226	6,746
Western Conference Teamsters [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	91-6145047
Pension Protection Act Zone Status	Green	Green
FIP/RP Status Pending/ Implemented	No
Contributions	2,315	2,180	1,943
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	1/12/15 to 6/30/19
IAM National [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	51-6031295
Pension Protection Act Zone Status	Green	Green
FIP/RP Status Pending/ Implemented	No
Contributions	3,311	2,987	2,038
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	9/14/15 to 9/30/19
Automobile Mechanics Local No. 701 [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	36-6042061
Pension Protection Act Zone Status	Red	Red
FIP/RP Status Pending/ Implemented	RP Adopted
Contributions	1,632	1,530	1,527
Surcharge Imposed	Yes
Expiration Date of Collective Bargaining Agreement	5/31/16 to 10/31/17
Central States Southwest and Southwest Areas [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	36-6044243
Pension Protection Act Zone Status	Red	Red
FIP/RP Status Pending/ Implemented	RP adopted
Contributions	211	226	226
Surcharge Imposed	No
Expiration Date of Collective Bargaining Agreement	10/31/15 to 5/31/17
Other Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 1,085	$ 1,483	$ 1,012