Credit Facility (Details) (USD $)	12 Months Ended				12 Months Ended			12 Months Ended					1 Months Ended
	Dec. 31, 2012 quarter	Dec. 31, 2011	Dec. 31, 2012 CRLLC	Dec. 31, 2012 CRNF	Dec. 31, 2012 CRNF Eurodollar	Apr. 13, 2011 CRNF Eurodollar Minimum	Apr. 13, 2011 CRNF Eurodollar Maximum	Dec. 31, 2012 CRNF Prime	Apr. 13, 2011 CRNF Prime Minimum	Apr. 13, 2011 CRNF Prime Maximum	Dec. 31, 2012 Term loan facility CRNF	Apr. 13, 2011 Term loan facility CRNF	Apr. 30, 2011 Revolving credit facility CRNF	Apr. 13, 2011 Revolving credit facility CRNF
Credit Facility
Borrowing capacity											$ 125,000,000	$ 125,000,000		$ 25,000,000
Uncommitted incremental facility													50,000,000
Amount of special distribution made by the Partnership to CRLLC upon closing of credit facility			87,200,000
Number of trailing quarters used in calculating the leverage ratio	4
Variable rate basis					Eurodollar rate			prime rate
Basis spread on variable rate (as a percent)					3.50%	3.50%	4.25%	2.50%	2.50%	3.25%
Lender and other third party costs incurred	4,824,000			4,800,000
Deferred financing costs
Deferred financing costs	4,824,000			4,800,000
Less accumulated amortization	1,660,000
Unamortized deferred financing costs	3,164,000
Less current portion	964,000	966,000
Unamortized deferred financing costs, noncurrent portion	2,200,000	3,164,000
Amortization of deferred financing costs reported as interest expense and other financing costs	$ 964,000	$ 694,000