Interest Rate Swap (Details) (CRNF, USD $) In Millions, unless otherwise specified			3 Months Ended
	Mar. 31, 2013 Term loan facility	Apr. 13, 2011 Term loan facility	Mar. 31, 2013 Designated as hedges Interest rate swap agreements entered into on June 30, 2011	Mar. 31, 2013 Designated as hedges Interest rate swap agreements entered into on July 1, 2011	Mar. 31, 2013 Designated as hedges Interest rate swap agreements	Mar. 31, 2012 Designated as hedges Interest rate swap agreements	Jul. 01, 2011 Designated as hedges Interest rate swap agreements item	Jun. 30, 2011 Designated as hedges Interest rate swap agreements item
Interest rate swap
Number of agreements							2	2
Borrowing capacity on credit facility	$ 125.0	$ 125.0
Aggregate notional amount					62.5
Floating rate basis			three month LIBOR	three month LIBOR	three month LIBOR
Fixed rate (as a percent)			1.94%	1.975%
Settlement period			90 days	90 days
Average fixed rate of interest (as a percent)					1.96%
Effective rate (as a percent)					4.58%
Interest expense re-classed from AOCI into earnings					$ 0.3	$ 0.2