Bank Loan Facilities - Additional Information (Details)		1 Months Ended	3 Months Ended
	Apr. 01, 2015 USD ($) Loan installment	Mar. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Feb. 29, 2016 USD ($)	Dec. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Term loan facility		$ 33,750,000	$ 33,750,000			$ 33,750,000
Cogent 12 Month Facility
Line of Credit Facility [Line Items]
Interest rate, percent	4.00%
Weighted average interest rate (percent)	0.75%	4.57%	4.57%
Term loan facility		$ 11,300,000	$ 11,300,000
Debt instrument term (years)	1 year
Cogent 36 Month Facility
Line of Credit Facility [Line Items]
Interest rate, percent	4.00%
Weighted average interest rate (percent)	1.25%	4.57%	4.57%
Term loan facility		$ 22,500,000	$ 22,500,000
Debt instrument term (years)	3 years
Number of semi-annual installments | installment	4
Debt instrument, amount outstanding to reduce interest rate	$ 7,500,000
Cogent 36 Month Facility | Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.75%
Cogent Partners, LP
Line of Credit Facility [Line Items]
Term loan facility	$ 45,000,000
Number of bank term loan facilities (loan) | Loan	2
Cogent Partners, LP | Cogent 12 Month Facility | Short-term Debt
Line of Credit Facility [Line Items]
Term loan facility	$ 22,500,000
Cogent Partners, LP | Cogent 36 Month Facility | Long-term Debt
Line of Credit Facility [Line Items]
Term loan facility	$ 22,500,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving loan facility, maximum borrowing capacity		70,000,000	$ 70,000,000		$ 50,000,000.0
Increase in maximum borrowing capacity		$ 20,000,000
Interest rate, percent		3.50%	3.50%
Weighted average daily borrowings outstanding under the loan facility			$ 40,300,000	$ 34,200,000
Weighted average interest rate (percent)		3.50%	3.50%	3.25%