Commitments and Contingencies Lease Contractual obligation (Details)		3 Months Ended
	Mar. 01, 2019 USD ($) ft²	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Leases [Abstract]
Operating Lease Term	5 years
Finance lease right-of-use assets		$ 22,700,000
Finance Lease, Right-of-Use Asset, Amortization		1,500,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months		41,500,000	$ 47,400,000
Capital Leases, Future Minimum Payments Due, Next Twelve Months		5,500,000	6,600,000
Operating Leases, Future Minimum Payments, Due in Two Years		48,400,000	38,400,000
Capital Leases, Future Minimum Payments Due in Two Years		6,300,000	5,400,000
Operating Leases, Future Minimum Payments, Due in Three Years		35,700,000	27,200,000
Capital Leases, Future Minimum Payments Due in Three Years		4,500,000	3,800,000
Operating Leases, Future Minimum Payments, Due in Four Years		24,500,000	17,900,000
Capital Leases, Future Minimum Payments Due in Four Years		2,700,000	2,100,000
Operating Leases, Future Minimum Payments, Due in Five Years		18,700,000	12,700,000
Capital Leases, Future Minimum Payments Due in Five Years		1,300,000	900,000
Operating Leases, Future Minimum Payments, Due Thereafter		18,600,000	16,100,000
Capital Leases, Future Minimum Payments Due Thereafter		12,900,000	12,800,000
Operating Leases, Future Minimum Payments Due		187,400,000	159,700,000
Capital Leases, Future Minimum Payments Due		33,200,000	31,600,000
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(16,700,000)
Finance Lease, Liability, Undiscounted Excess Amount		4,600,000
Capital Leases, Future Minimum Payments, Interest Included in Payments			2,100,000
Operating Lease, Liability		170,700,000
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments		28,600,000	29,500,000
Finance Lease, Interest Expense		200,000
Operating Lease, Cost		14,800,000
Short-term Lease, Cost		1,100,000
Variable Lease, Cost		4,500,000
Lease, Cost		22,100,000
Operating lease right-of-use assets		170,100,000	0
Finance lease liability, current		6,300,000
Finance lease liability, non-current		22,300,000
Operating lease liability, current		48,100,000	0
Operating lease liability, non-current		$ 122,600,000	$ 0
Weighted-average remaining lease term - finance leases		5 years 5 months 15 days
Weighted-average remaining lease term - operating leases		4 years 4 months 13 days
Weighted-average discount rate - finance leases		2.23%
Weighted-average discount rate – operating leases		4.05%
Area of Leased Office Building | ft²	192,000
Purchase Price of Property at End of Lease Term	$ 41,200,000
Percentage of Lease Balance as Final Payment End of Lease Term	87.00%
debt instrument, Covenant for debt not paid	$ 75,000,000
Operating cash flows from finance leases		$ 1,000,000.0
Operating cash flows from operating leases		12,700,000
Financing cash flows from finance leases		1,600,000
Right-of-use assets obtained in exchange for new finance lease liabilities		3,200,000
Right-of-use assets obtained in exchange for new operating lease liabilities		$ 16,600,000