14. Leases (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 11,100	$ 11,100
Finance Lease, Liability, Payments, Remainder of Fiscal Year	$ 1,200	$ 1,200
Operating Lease, Weighted Average Remaining Lease Term	9 years	9 years
Finance Lease, Weighted Average Remaining Lease Term	18 years	18 years
Operating Lease, Weighted Average Discount Rate, Percent	4.30%	4.30%
Property, plant and equipment, gross	$ 1,347,364	$ 1,347,364	$ 1,326,829
Operating Leases, Future Minimum Payments Due, Next Twelve Months			44,400
Operating Leases, Future Minimum Payments, Due in Two Years			37,800
Operating Leases, Future Minimum Payments, Due in Three Years			27,400
Operating Leases, Future Minimum Payments, Due in Four Years			19,700
Operating Leases, Future Minimum Payments, Due in Five Years			13,900
Operating Leases, Future Minimum Payments, Due Thereafter			25,600
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals			17,800
Less: accumulated depreciation and amortization	(851,488)	(851,488)	(818,139)
Property, plant and equipment, net	495,876	495,876	508,690
Finance Lease, Liability, Current	500	500
Finance Lease, Liability, Noncurrent	11,200	11,200
Finance Lease, Liability	$ 11,700	$ 11,700
Finance Lease, Weighted Average Discount Rate, Percent	6.50%	6.50%
Lessee, Operating Lease, Liability, Payments, Due Year Two	$ 41,000	$ 41,000
Finance Lease, Liability, Payments, Due Year Two	1,300	1,300
Lessee, Operating Lease, Liability, Payments, Due Year Three	35,400	35,400
Finance Lease, Liability, Payments, Due Year Three	1,200	1,200
Lessee, Operating Lease, Liability, Payments, Due Year Four	27,900	27,900
Finance Lease, Liability, Payments, Due Year Four	1,100	1,100
Lessee, Operating Lease, Liability, Payments, Due Year Five	24,300	24,300
Finance Lease, Liability, Payments, Due Year Five	1,100	1,100
Lessee, Operating Lease, Liability, Payments, Due after Year Five	141,300	141,300
Finance Lease, Liability, Payments, Due after Year Five	15,400	15,400
Lessee, Operating Lease, Liability, Payments, Due	281,000	281,000
Finance Lease, Liability, Payment, Due	21,300	21,300
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(54,700)	(54,700)
Capital Leases, Future Minimum Payments Due, Next Twelve Months			500
Capital Leases, Future Minimum Payments Due in Two Years			200
Capital Leases, Future Minimum Payments Due in Three Years			500
Capital Leases, Future Minimum Payments Due in Four Years			400
Capital Leases, Future Minimum Payments Due in Five Years			400
Capital Leases, Future Minimum Payments Due Thereafter			9,900
Finance Lease, Liability, Undiscounted Excess Amount	(9,600)	(9,600)
Operating lease right-of-use assets	217,516	217,516	0
Operating Lease, Payments	11,600	34,500
Operating Lease, Cost	14,200	38,700
Finance Lease, Right-of-Use Asset, Amortization	100	500
Finance Lease, Interest Expense	200	700
Finance Lease Cost	300	1,200
Sublease Income	700	2,200
Finance Lease, Interest Payment on Liability	200	700
Finance Lease, Principal Payments	100	500
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	14,400	20,200
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	100	100
Current operating lease liabilities	33,694	33,694	0
Operating lease liabilities	192,600	192,600	$ 0
Operating Lease, Liability	226,300	$ 226,300
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee Operating And Finance Leases Remaining Lease Term		1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee Operating And Finance Leases Remaining Lease Term		20 years
Finance Lease [Member]
Lessee, Lease, Description [Line Items]
Property, plant and equipment, gross	11,400	$ 11,400
Less: accumulated depreciation and amortization	(4,000)	(4,000)
Property, plant and equipment, net	$ 7,400	$ 7,400