Long-Term Debt (BOA) (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Feb. 12, 2014 USD ($)
Long-Term Debt
Total long-term debt	$ 177,950,000	$ 163,194,000
Credit Agreement | Bank of America, N.A
Long-Term Debt
Unused balance	78,150,000
Available borrowings	$ 19,850,000
Commitment fee on the unused commitments (as a percent)	0.50%
Credit Agreement | Bank of America, N.A | Minimum | After the closing of the IPO
Long-Term Debt
Available Liquidity Covenant	$ 25,000,000
Consolidated interest coverage ratio	2.50
Credit Agreement | Bank of America, N.A | Maximum | After the closing of the IPO
Long-Term Debt
Consolidated total leverage ratio prior to the issuance of certain unsecured notes	4.50
Consolidated total leverage ratio after the issuance of certain unsecured notes	5.00
Consolidated senior secured leverage ratio after the issuance of certain unsecured notes	3.50
Credit Agreement | Bank of America, N.A | Federal funds effective rate
Long-Term Debt
Interest rate spread (as a percent)	0.50%
Credit Agreement | Bank of America, N.A | LIBOR
Long-Term Debt
Interest rate spread (as a percent)	1.00%
Initial applicable margin (as a percent)	2.25%
Credit Agreement | Bank of America, N.A | Prime rate
Long-Term Debt
Initial applicable margin (as a percent)	1.25%
Revolving loans | Bank of America, N.A
Long-Term Debt
Total long-term debt	$ 177,000,000	162,000,000
Revolving loans | Credit Agreement | Bank of America, N.A
Long-Term Debt
Maximum borrowing capacity		275,000,000	$ 275,000,000
Letters of credit | Credit Agreement | Bank of America, N.A | Maximum
Long-Term Debt
Maximum borrowing capacity			$ 100,000,000
Noncompete notes payable
Long-Term Debt
Total long-term debt		$ 117,000