Guarantees	12 Months Ended
Dec. 31, 2011
Guarantees [Abstract]
Guarantees	NOTE 13. Guarantees In 2008 the California Air Resources Board (CARB) approved regulations that require significantly reduced emissions from existing on-road diesel vehicles operating in California. The regulations require older model tractors to be modified to comply with the new regulations. In response to the costs associated with complying with these new emission laws, we developed a guaranty program with a leasing company. As part of this program, we are guaranteeing certain owner operators' lease payments for these tractors. The guarantees expire at various dates beginning in 2012 thru 2017. The potential maximum exposure under these lease guarantees was approximately $24.0 million and $6.8 million as of December 31, 2011 and 2010, respectively. The potential maximum exposure represents the amount of the remaining lease payments on all outstanding guaranteed leases as of December 31, 2011 and 2010. However, upon default, we have the option to purchase the tractors. We could then sell the tractors and use the proceeds to recover all or a portion of the amounts paid under the guarantees. Alternatively, we can contract with another owner operator who would assume the lease. There were no material defaults during the years ended December 31, 2011 and 2010 and no potential material defaults. We had a liability of approximately $0.5 million at December 31, 2011 and $0.1 million as of December 31, 2010, for the guarantees representing the fair value of the guarantees based on a discounted cash-flow analysis included in non-current liabilities in our Consolidated Balance Sheet. We are amortizing the amounts over the remaining lives of the respective guarantees.

NOTE 13. Guarantees

In 2008 the California Air Resources Board (CARB) approved regulations that require significantly reduced emissions from existing on-road diesel vehicles operating in California. The regulations require older model tractors to be modified to comply with the new regulations. In response to the costs associated with complying with these new emission laws, we developed a guaranty program with a leasing company. As part of this program, we are guaranteeing certain owner operators' lease payments for these tractors. The guarantees expire at various dates beginning in 2012 thru 2017.

The potential maximum exposure under these lease guarantees was approximately $24.0 million and $6.8 million as of December 31, 2011 and 2010, respectively. The potential maximum exposure represents the amount of the remaining lease payments on all outstanding guaranteed leases as of December 31, 2011 and 2010. However, upon default, we have the option to purchase the tractors. We could then sell the tractors and use the proceeds to recover all or a portion of the amounts paid under the guarantees. Alternatively, we can contract with another owner operator who would assume the lease. There were no material defaults during the years ended December 31, 2011 and 2010 and no potential material defaults.

We had a liability of approximately $0.5 million at December 31, 2011 and $0.1 million as of December 31, 2010, for the guarantees representing the fair value of the guarantees based on a discounted cash-flow analysis included in non-current liabilities in our Consolidated Balance Sheet. We are amortizing the amounts over the remaining lives of the respective guarantees.