Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory federal tax rate		21.00%	21.00%	35.00%
Income Tax Expense (Benefit)		$ 197,437,000	$ 363,969,000	$ 129,439,000
Income Tax Expense (Benefit) Due to Tax Reform	$ (180,600,000)
Deferred Tax Assets, Valuation Allowance		21,958,000	21,788,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		6,000,000.0	6,000,000.0
Benefits (Expenses) from the decrease (increase) of interest expense		(400,000)	(1,300,000)	85,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		1,400,000	$ 2,400,000
Minimum
Income Tax Examination, Estimate of Possible Loss		0
Maximum
Income Tax Examination, Estimate of Possible Loss		3,300,000
Domestic Tax Authority [Member]
Income Tax Expense (Benefit) Due to Tax Reform				(182,500,000)
Operating Loss Carryforwards		$ 91,600,000
Foreign Tax Authority [Member]
Income Tax Expense (Benefit) Due to Tax Reform				$ 1,900,000