Short-Term Borrowing Short-Term Borrowing - Schedule of Short-Term Debt (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 370,000
Long-term Line of Credit		290,103	$ 240,671
Line of Credit Facility, Remaining Borrowing Capacity		79,897
Bank Overdrafts	[1]	4,355	10,298
Short-term borrowing		294,458	250,969
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
Line of Credit Facility, Remaining Borrowing Capacity		$ 30,000
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 1.00 percent
Short-term Revolving Line of Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 50,000
Long-term Line of Credit			50,000
Debt Instrument, Description of Variable Rate Basis		Lender's base rate plus 80 basis points
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		40,000	40,171
Line of Credit Facility, Remaining Borrowing Capacity		$ 10,328
Debt Instrument, Description of Variable Rate Basis		Lender's base rate, plus 0.85 percent
Committed Line of Credit Facility Five [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 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	[2]		75,000
Line of Credit Facility, Remaining Borrowing Capacity	[2]	$ 25,000
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 1.00 percent
Committed Line of Credit Facility Two [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 30,000
Long-term Line of Credit			$ 20,500
Line of Credit Facility, Remaining Borrowing Capacity		$ 14,569
Debt Instrument, Description of Variable Rate Basis		LIBOR rate, plus 1.00 percent

[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 $200.0 million.