Share-Based Compensation (Share-Based Compensation Arrangement Expenses Recognized) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Share-Based Compensation [Abstract]
Salaries, wages and employee benefits	$ 5,062	$ 4,763
Deferred income tax benefit	(1,965)	(1,844)
Net share-based compensation expense	$ 3,097	$ 2,919

Employee Service Share Based Compensation Deferred Tax Benefit From Compensation Expense

No definition available.

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Namespace Prefix:	cnw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration