Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Tax Cuts and Jobs Act, Change in Tax Rate, Deferred Tax Liability, Income Tax Benefit	$ 153,300,000
Tax Cuts and Jobs Act, Decrease in Deferred Tax Liability due to Transition Tax	$ 28,300,000
Deferred income tax expense (benefit)		$ 69,751,000	$ (7,123,000)	$ (146,452,000)
Deferred state income tax asset		51,608,000	34,107,000
Deferred tax assets with respect to U.S. Federal income tax loss carryforwards		1,765,000	2,100,000
Deferred tax assets with respect to non U.S. income tax loss carryforwards		15,214,000	15,868,000
Valuation Allowance, Amount		46,243,000	33,120,000
Deferred income tax liabilities related to undistributed earnings of investments in non-U.S. subsidiaries		1,670,000	1,726,000
Interest accrued related to unrecognized tax benefits		800,000
Penalties accrued related to unrecognized tax benefits		0
State [Member]
Income Taxes [Line Items]
Income tax loss carryforwards to expire		849,300,000
Deferred state income tax asset		51,600,000
Non-U.S.deferred tax asset related to capital loss carryforwards		307,000	1,093,000
Valuation Allowance, Amount		34,000,000.0
Valuation allowance related to operating loss carryforwards		29,800,000
Valuation allowance released		11,632,000	(15,767,000)	(946,000)
Unrecognized tax benefit that would impact the effective tax rate		1,600,000
State [Member] | Education [Member]
Income Taxes [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			20,000,000.0
U.S. Federal [Member]
Income Taxes [Line Items]
Income tax loss carryforwards obtained as a result of prior stock acqusitions		8,400,000
Deferred tax assets with respect to U.S. Federal income tax loss carryforwards		1,800,000
Foreign tax credit carryforwards		700,000
Deferred tax assets with respect to U.S. Federal foreign tax credit carryforwards		717,000	987,000
Tax Credit Carryforward, Valuation Allowance		700,000
Federal tax impact of unrecognized tax benefits that would impact the effective tax rate		300,000
non-U.S. [Member]
Income Taxes [Line Items]
Tax loss carryforwards as a result of operating losses and prior stock acquisitions		57,800,000
Deferred tax assets with respect to non U.S. income tax loss carryforwards		15,200,000
Valuation allowance against the deferred tax assets recorded for the tax losses carryforward		7,400,000
Tax loss carryforwards from operating losses and prior stock acquisitions that can be carried forward indefinitely		38,500,000
Non-U.S.deferred tax asset related to capital loss carryforwards		3,583,000	3,609,000
Valuation Allowance, Amount		11,400,000
Valuation allowance released		1,202,000	$ 1,322,000	$ (1,935,000)
non-U.S. [Member] | Through 2024 [Member]
Income Taxes [Line Items]
Tax loss carryforwards subject to expiration		13,800,000
non-U.S. [Member] | After 2024 [Member]
Income Taxes [Line Items]
Tax loss carryforwards subject to expiration		5,500,000
Capital loss carryforward [Member] | non-U.S. [Member]
Income Taxes [Line Items]
Carryforward amount		12,000,000.0
Valuation Allowance, Amount		$ 3,600,000