Unsecured Revolving Credit Facility (Tables)
 3 Months Ended
Mar. 31, 2012
Unsecured Revolving Credit Facility [Abstract]  
Change In The Operating Partnership's Unsecured Debt Ratings
Operating Partnership's
Interest Rate –
  
Unsecured Debt Ratings:
Applicable Basis Points
Facility Fee
Higher of S&P or Moody's
Above LIBOR
Basis Points
No ratings or less than BBB-/Baa3
185.0
45.0
BBB- or Baa3
150.0
35.0
BBB or Baa2(current)
125.0
25.0
BBB+or  Baa1
107.5
20.0
A-or A3 or higher
100.0
17.5