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Income Taxes (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provisional one-time net benefit from changes in U.S. tax laws		$ 194,100,000
Changes in provisional amount of initial one-time benefit recorded resulting from change in U.S. tax laws	$ 0

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- Definition

Tax Cuts And Jobs Act Of 2017, Measurement Period Adjustment, Income Tax Expense (Benefit)

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- Definition

Tax Cuts And Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)

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