Unsecured Revolving Credit Facility And Term Loans (Schedule Of Interest Rates On Outstanding Borrowings, Alternate Base Rate Loans, And Facility Fee) (Details)	3 Months Ended
	Mar. 31, 2018
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
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)
Baa2 [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB or Baa2
Baa1 [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB+ or Baa1
A3 Or Higher [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	A- or A3 or higher
2017 Credit Facility [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	1.20%
Facility Fee Basis Points	0.25%
2017 Credit Facility [Member] | 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
Interest Rate - Applicable Basis Points Above LIBOR	1.55%
Facility Fee Basis Points	0.30%
2017 Credit Facility [Member] | 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)
Interest Rate - Applicable Basis Points Above LIBOR	1.20%
Facility Fee Basis Points	0.25%
2017 Credit Facility [Member] | Baa2 [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB or Baa2
Interest Rate - Applicable Basis Points Above LIBOR	1.00%
Facility Fee Basis Points	0.20%
2017 Credit Facility [Member] | Baa1 [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Unsecured Debt Ratings	BBB+ or Baa1
Interest Rate - Applicable Basis Points Above LIBOR	0.90%
Facility Fee Basis Points	0.15%
2017 Credit Facility [Member] | A3 Or Higher [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	0.875%
Facility Fee Basis Points	0.125%
2017 Credit Facility [Member] | Base Rate [Member] | No Ratings Or Less Than Baa3 [Member] | No Ratings Or Less Than BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.55%
2017 Credit Facility [Member] | Base Rate [Member] | Baa3 [Member] | BBB- [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.20%
2017 Credit Facility [Member] | Base Rate [Member] | Baa2 [Member] | BBB [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.00%
2017 Credit Facility [Member] | Base Rate [Member] | Baa1 [Member] | BBB+ [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.00%
2017 Credit Facility [Member] | Base Rate [Member] | A3 Or Higher [Member] | A- Or Higher [Member]
Line of Credit Facility [Line Items]
Interest Rate - Applicable Basis Points Above LIBOR	0.00%