Derivative Instruments And Hedging Activities Interest Rate Swaps (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Interest expense	$ 32,399	$ 28,731	$ 97,446	$ 85,534

Amount of the cost of borrowed funds accounted for as interest expense.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration