Unsecured Revolving Credit Facility And Term Loans (Schedule Of Interest Rate On Outstanding Borrowings Payable) (Details)	9 Months Ended
	Sep. 30, 2018
2017 Term Loan [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.55%
2016 Term Loan [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.55%
No Ratings Or Less Than Baa3 [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	No ratings or less than BBB-/Baa3
No Ratings Or Less Than Baa3 [Member] | 2017 Term Loan [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	No ratings or less than BBB-/Baa3
Interest Rate - Applicable Basis Points Above LIBOR	1.85%
No Ratings Or Less Than Baa3 [Member] | 2016 Term Loan [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.85%
Baa3 [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB- or Baa3 (interest rate based on Company's election through March 5, 2018)
Baa3 [Member] | 2017 Term Loan [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB- or Baa3 (interest rate based on Company's election through March 5, 2018)
Interest Rate - Applicable Basis Points Above LIBOR	1.40%
Baa3 [Member] | 2016 Term Loan [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.40%
Baa2 [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB or Baa2
Baa2 [Member] | 2017 Term Loan [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB or Baa2
Interest Rate - Applicable Basis Points Above LIBOR	1.15%
Baa2 [Member] | 2016 Term Loan [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.15%
Baa1 [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB+ or Baa1
Baa1 [Member] | 2017 Term Loan [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB+ or Baa1
Interest Rate - Applicable Basis Points Above LIBOR	1.00%
Baa1 [Member] | 2016 Term Loan [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.00%
A3 Or Higher [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	A- or A3 or higher
A3 Or Higher [Member] | 2017 Term Loan [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	A- or A3 or higher
Interest Rate - Applicable Basis Points Above LIBOR	0.90%
A3 Or Higher [Member] | 2016 Term Loan [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.90%
Base Rate [Member] | No Ratings Or Less Than Baa3 [Member] | 2017 Term Loan [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.85%
Base Rate [Member] | Baa3 [Member] | 2017 Term Loan [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.40%
Base Rate [Member] | Baa2 [Member] | 2017 Term Loan [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.15%
Base Rate [Member] | Baa1 [Member] | 2017 Term Loan [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.00%
Base Rate [Member] | A3 Or Higher [Member] | 2017 Term Loan [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.00%