Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Write-off of deferred taxes related to intercompany loans			$ 0	$ 0	$ 10,965,000
Deferred income tax expense (benefit)			(7,123,000)	(146,452,000)	10,070,000
Deferred state income tax asset	$ 35,434,000		34,107,000	35,434,000
Deferred tax assets with respect to U.S. Federal income tax loss carryforwards	2,857,000		2,100,000	2,857,000
Deferred tax assets with respect to non U.S. income tax loss carryforwards	18,797,000		15,868,000	18,797,000
Valuation Allowance, Amount	48,742,000		33,120,000	48,742,000
Deferred income tax liabilities related to undistributed earnings of investments in non-U.S. subsidiaries	1,606,000		1,726,000	1,606,000
Interest accrued related to unrecognized tax benefits			600,000
Penalties accrued related to unrecognized tax benefits			0
Reduction In Federal Tax Rate [Member]
Income Taxes [Line Items]
Income Tax Expense (Benefit), Adjustment of Deferred Tax (Asset) Liability	153,300,000
Change in Tax on non-US Subsidiary Earnings [Member]
Income Taxes [Line Items]
Income Tax Expense (Benefit), Adjustment of Deferred Tax (Asset) Liability	28,300,000
Adjustment [Member]
Income Taxes [Line Items]
Deferred income tax expense (benefit)					(5,600,000)
State [Member]
Income Taxes [Line Items]
Income tax loss carryforwards to expire			698,900,000
Deferred state income tax asset			34,100,000
Non-U.S.deferred tax asset related to capital loss carryforwards	0		1,093,000	0
Valuation Allowance, Amount			22,200,000
Valuation allowance related to operating loss carryforwards			17,900,000
Valuation allowance released			(15,767,000)	(946,000)	3,196,000
Unrecognized tax benefit that would impact the effective tax rate			2,500,000
State [Member] | Education [Member]
Income Taxes [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount			(20,000,000)
U.S. Federal [Member]
Income Taxes [Line Items]
Income tax loss carryforwards obtained as a result of prior stock acqusitions			9,900,000
Deferred tax assets with respect to U.S. Federal income tax loss carryforwards			2,100,000
Foreign tax credit carryforwards			1,000,000
Deferred tax assets with respect to U.S. Federal foreign tax credit carryforwards	2,522,000		987,000	2,522,000
Federal tax impact of unrecognized tax benefits that would impact the effective tax rate			500,000
non-U.S. [Member]
Income Taxes [Line Items]
Tax loss carryforwards as a result of operating losses and prior stock acquisitions			58,100,000
Deferred tax assets with respect to non U.S. income tax loss carryforwards			15,900,000
Valuation allowance against the deferred tax assets recorded for the tax losses carryforward			6,100,000
Tax loss carryforwards from operating losses and prior stock acquisitions that can be carried forward indefinitely			46,800,000
Non-U.S.deferred tax asset related to capital loss carryforwards	2,336,000		3,609,000	2,336,000
Valuation Allowance, Amount			9,900,000
Valuation allowance released			1,322,000	(1,935,000)	$ (12,688,000)
non-U.S. [Member] | Through 2023 [Member]
Income Taxes [Line Items]
Tax loss carryforwards subject to expiration			8,400,000
non-U.S. [Member] | After 2023 [Member]
Income Taxes [Line Items]
Tax loss carryforwards subject to expiration			2,900,000
U.S. Federal and State [Member]
Income Taxes [Line Items]
Excess of book value over tax basis of investment	113,200,000		226,100,000	113,200,000
Australian Taxation Office [Member]
Income Taxes [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		$ 19,300,000
Capital loss carryforwards to 2013 tax year [Member] | Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Refund from Settlement with Taxing Authority	$ 9,700,000			$ 9,700,000
Capital loss carryforward [Member] | non-U.S. [Member]
Income Taxes [Line Items]
Carryforward amount			12,000,000
Valuation Allowance, Amount			$ 3,600,000