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Debt And Liquidity (Narrative) (Details) - USD ($)			6 Months Ended
Debt And Liquidity (Narrative) (Details) - USD ($)	Apr. 19, 2018	Feb. 12, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Jun. 15, 2018	Mar. 31, 2018	Dec. 31, 2017	Nov. 20, 2012
Debt Instrument [Line Items]
Long-term Debt			$ 2,034,807,000		$ 2,156,634,000
Stated interest rate								6.375%
Loan balance, net of unamortized discount			$ 43,462,000		$ 106,323,000
Equity interest pledge			65.00%
Senior Notes
Debt Instrument [Line Items]
Principal amount issued									$ 300,000,000
Stated interest rate									6.375%
Debt Instrument, Redemption Price, Percentage				101.594%
2018 Credit Agreement
Debt Instrument [Line Items]
Leverage ratio			4.00
Revolving Credit Facility \| Amended and Restated Credit Agreement July 2015
Debt Instrument [Line Items]
Long-term Line of Credit								$ 39,500,000
Outstanding letters of credit								8,700,000
Revolving Credit Facility \| 2018 Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity		$ 250,000,000				$ 2,250,000,000	$ 1,500,000,000
Borrowing threshold (greater than)			$ 35,000,000
Borrowing threshold percentage			35.00%
Increase in borrowing capacity						$ 750,000,000
Debt instrument, upfront fees						1.00%
Revolving Credit Facility \| 2018 Revolving Credit Facility \| LIBO
Debt Instrument [Line Items]
Margin spread on variable interest rate		3.75%
Revolving Credit Facility \| 2018 Revolving Credit Facility \| ABR
Debt Instrument [Line Items]
Margin spread on variable interest rate		2.75%
Term Loan Facility \| Amended and Restated Credit Agreement July 2015
Debt Instrument [Line Items]
Long-term Line of Credit								$ 18,700,000
Line of Credit \| 2018 Term Loan Facility
Debt Instrument [Line Items]
Borrowing capacity		$ 1,500,000,000
Margin spread on variable interest rate			0.25%
Debt Instrument, Amortization Rate			5.00%
Prepayment premium			1.00%
Excess Cashflow Threshold Percentage			75.00%
Line of Credit \| 2018 Term Loan Facility \| Contingent Event One
Debt Instrument [Line Items]
Excess Cashflow Threshold Percentage			50.00%
Line of Credit \| 2018 Term Loan Facility \| Contingent Event Two
Debt Instrument [Line Items]
Excess Cashflow Threshold Percentage			0.00%
Leverage ratio			1.25
Line of Credit \| 2018 Term Loan Facility \| Minimum \| Contingent Event One
Debt Instrument [Line Items]
Leverage ratio			1.25
Line of Credit \| 2018 Term Loan Facility \| Maximum \| Contingent Event One
Debt Instrument [Line Items]
Leverage ratio			1.75
Line of Credit \| 2018 Term Loan Facility \| LIBO
Debt Instrument [Line Items]
Margin spread on variable interest rate		3.50%
Undrawn commitment fee		0.25%
Line of Credit \| 2018 Term Loan Facility \| ABR
Debt Instrument [Line Items]
Margin spread on variable interest rate		2.50%
Brookfield \| Brookfield Promissory Note [Member]
Debt Instrument [Line Items]
Dividends Payable	$ 750,000,000
Brookfield \| Brookfield Promissory Note [Member] \| Maximum
Debt Instrument [Line Items]
Leverage ratio	175.00%
Brookfield \| Brookfield Promissory Note [Member] \| LIBO
Debt Instrument [Line Items]
Margin spread on variable interest rate	4.50%
Third Anniversary \| Brookfield \| Brookfield Promissory Note [Member] \| LIBO
Debt Instrument [Line Items]
Margin spread on variable interest rate	2.00%