Subsequent Events (Details) - USD ($)			6 Months Ended
	Jul. 19, 2017	Jul. 18, 2017	Jul. 01, 2017
Line of Credit | Private Bank, Trust Company and BMO Harris Bank N A | Subsequent Event
Subsequent Events
Terms notes, available borrowing to fund Tender Offer		$ 15,000,000
Line of Credit | Private Bank, Trust Company and BMO Harris Bank N A | Tender Offer | Subsequent Event
Subsequent Events
Shares authorized for repurchase		400,000
Purchase of stock, price per share		$ 124.48
Notes Payable, Other Payables | Prudential Investment Management, Inc
Subsequent Events
Term note, face value			$ 25,000,000
Term of notes payable			10 years
Interest			5.50%
Minimum prepayment			$ 1,000,000
Notes Payable, Other Payables | Prudential Investment Management, Inc | Subsequent Event
Subsequent Events
Term note, face value	$ 12,500,000
Term of notes payable	10 years
Interest	5.10%
Quarterly principal payment	$ 312,500
Minimum prepayment	$ 1,000,000