Commitments and Contingencies - Litigation (Details) $ in Millions		1 Months Ended	4 Months Ended	12 Months Ended
	Dec. 31, 2007	Apr. 25, 2019 USD ($)	Apr. 25, 2019 lawsuit	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)
Call Option Lawsuits | Subsequent Event
Loss Contingencies [Line Items]
Number of lawsuits filed | lawsuit			9
CRNF
Loss Contingencies [Line Items]
Property tax abatement period	10 years
Increase in property tax expense (in excess of)				$ 10.0	$ 10.0	$ 10.0	$ 10.0	$ 10.0
CRNF | Subsequent Event
Loss Contingencies [Line Items]
Litigation settlement agreement, recovery amount		$ 7.9