Capital Leases (Narrative) (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Capital Leased Assets [Line Items]
Revenue equipment cost	$ 316,200,000
Accumulated amortization	140,300,000
Obligations under capital leases	134,700,000	148,700,000
Capital leases obligations, current	$ 39,375,000	$ 52,700,000