Interest Rate Swap Agreements (Details) - CRNF	12 Months Ended
	Dec. 31, 2016 USD ($) agreement	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Term loan facility
Interest rate swap
Debt instrument face amount	$ 125,000,000
Designated as hedges | Interest rate swap agreements
Interest rate swap
Number of agreements | agreement	2
Aggregate notional amount	$ 62,500,000.0
Average fixed rate of interest (as a percent)	1.96%
Gain (loss) reclassified from earnings	$ (100,000)	$ 1,100,000	$ 1,100,000
Designated as hedges | Interest rate swap agreements entered into on June 30, 2011
Interest rate swap
Fixed rate (as a percent)	1.94%
Settlement period (in days)	90 days
Designated as hedges | Interest rate swap agreements entered into on July 1, 2011
Interest rate swap
Fixed rate (as a percent)	1.975%
Settlement period (in days)	90 days