Credit Facility (Details)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Revolving credit facility [Member]
Line of Credit Facility [Line Items]
Debt term	5 years
Borrowing capacity	$ 150,000,000.0
Potential maximum borrowing capacity	200,000,000
Amounts outstanding	$ 0	$ 0
Minimum interest coverage ratio for four consecutive fiscal quarters	4.00
Leverage ratio	3.00
Standby letters of credit [Member]
Line of Credit Facility [Line Items]
Borrowing capacity	$ 7,500,000.0
Minimum [Member] | Revolving credit facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	0.75%
Commitment fee on undrawn amounts	0.30%
Maximum [Member] | Revolving credit facility [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	2.25%
Commitment fee on undrawn amounts	0.45%