Fair Value Disclosures (Assets and Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018	Jul. 26, 2018
Long-term Debt		$ 3,101,611	$ 2,986,054
Net Investment in Direct Financing and Sales Type Leases		20,727	20,558	$ 37,900
Derivative Asset, Fair Value, Gross Asset		3,600	10,600
Derivative Liability, Fair Value, Gross Liability		6,000	0
Fair Value, Recurring [Member] | Cross Currency Swaps [Member]
Derivative Asset, Fair Value, Gross Asset	[1]	3,646	6,278
Fair Value, Recurring [Member] | Cross Currency Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset, Fair Value, Gross Asset	[1]	3,646	6,278
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Derivative Asset, Fair Value, Gross Asset	[1]		(4,344)
Derivative Liability, Fair Value, Gross Liability	[2]	5,966
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset, Fair Value, Gross Asset	[1]		(4,344)
Derivative Liability, Fair Value, Gross Liability	[2]	5,966
Imagine Schools Remaining in DFL [Member]
Net Investment in Direct Financing and Sales Type Leases		20,700	20,600
Variable Rate Converted to Fixed Rate [Member]
Long-term Debt		$ 425,000	$ 350,000

[1] Included in "Other assets" in the accompanying consolidated balance sheets.

[2] Included in "Accounts payable and accrued liabilities" in the accompanying consolidated balance sheets.