Short-Term Borrowing Short-Term Borrowing - Schedule of Short-Term Debt (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Short-term Debt [Line Items]
Short-term Debt, Maximum Amount Outstanding During Period		$ 250,000
Line of Credit Facility, Maximum Borrowing Capacity		370,000
Long-term Line of Credit		244,190	$ 290,103
Line of Credit Facility, Remaining Borrowing Capacity		125,810
Bank Overdrafts	[1]	3,181	4,355
Short-term borrowing		$ 247,371	294,458
Number Of Unsecured Bank Credit Facilities		4
Committed Line of Credit Facility One [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 55,000
Long-term Line of Credit		55,000	25,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 0
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 0.75 percent
Committed Line of Credit Facility Three [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 45,000
Long-term Line of Credit		42,040	34,672
Line of Credit Facility, Remaining Borrowing Capacity		$ 2,960
Debt Instrument, Description of Variable Rate Basis		Lender's base rate, plus 0.75 percent
Committed Line of Credit Facility Five [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 40,000
Long-term Line of Credit		40,000	40,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 0
Debt Instrument, Description of Variable Rate Basis		Lender's base rate, plus 0.85 percent
Committed Line of Credit Facility Four [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[2]	$ 150,000
Long-term Line of Credit		50,000	125,000
Line of Credit Facility, Remaining Borrowing Capacity	[2]	$ 100,000
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 1.125 percent
Committed Line of Credit Facility Two [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 80,000
Long-term Line of Credit		57,150	$ 65,431
Line of Credit Facility, Remaining Borrowing Capacity		$ 22,850
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 0.75 percent

[1] ⁽¹⁾ If presented, these book overdrafts would be funded through the bank revolving credit facilities.

[2] This committed revolving credit facility includes a restriction that our short-term borrowings, excluding any borrowings under the committed revolving credit facility, shall not exceed $250.0 million.