Debt (Narrative) (Details) - USD ($)		12 Months Ended
	Feb. 27, 2017	Dec. 31, 2016	Jun. 30, 2017
Debt Instrument [Line Items]
Short-term debt outstanding			$ 15,000,000
Letter of Credit [Member]
Debt Instrument [Line Items]
New credit facility amount			55,400,000
Credit facility, maximum borrowing capacity			215,200,000
Term Loan A [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		$ 600,000,000	600,000,000
Term Loan B [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		$ 250,000,000	250,000,000
Bank, legal and other fees	$ 600,000
Term Loan B [Member] | LIBOR
Debt Instrument [Line Items]
Interest rate spread	2.75%	3.25%
Bi-lateral Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
New credit facility amount			19,200,000
Credit facility, maximum borrowing capacity		$ 25,000,000	25,000,000
Tax-Exempt Industrial Development Bond [Member]
Debt Instrument [Line Items]
Long-term debt outstanding		35,000,000	35,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		200,000,000	200,000,000
Letter of credit maximum sublimit		150,000,000	150,000,000
Short-term debt outstanding		0	15,000,000
Securitization Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
New credit facility amount			36,200,000
Credit facility, maximum borrowing capacity			40,000,000
Letters of credits issued classified as restricted cash		4,000,000	0
Senior Credit Facility [Member]
Debt Instrument [Line Items]
New credit facility amount		$ 1,050,000,000	$ 1,050,000,000