Annual report pursuant to Section 13 and 15(d)

Notes Payable (Details)

v2.4.0.8
Notes Payable (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2013
Unsecured Debt [Member]
Mar. 15, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 5.125% [Member]
Dec. 31, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 5.34% [Member]
Dec. 31, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 5.359% [Member]
Dec. 31, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 5.49% [Member]
Dec. 31, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 5.053% [Member]
Dec. 31, 2013
Unsecured Debt [Member]
10 Year Unsecured Notes 3.950 % [Member]
Dec. 31, 2013
Unsecured Debt [Member]
20 Year Unsecured Notes [Member]
Dec. 31, 2013
Subsequent Event [Member]
Unsecured Debt [Member]
10 Year Unsecured Notes 5.34% [Member]
Debt Instrument [Line Items]                      
Coupon stated rate       5.125% [1] 5.25% 5.35% 5.35% 4.95% 3.95% 7.25%  
Effective rate           5.359% [1] 5.49% [1] 5.053% [1] 4.018% [1] 7.36% [1] 5.339% [1]
Total principal $ 297,200   $ 850,000                
Net unamortized discount     (3,297)                
Notes Payable $ 846,703 $ 906,190 $ 846,703 $ 60,000   $ 50,000 $ 100,000 $ 250,000 $ 300,000 $ 50,000 $ 100,000
Debt Instrument, Maturity Date         Jan. 15, 2014 [2] May 01, 2015 [2] May 01, 2015 [2] Oct. 01, 2020 [2] Oct. 15, 2022 [2] Feb. 25, 2028 [2]  
[1] Yield on issuance date, including the effects of discounts on the notes.
[2] No principal amounts are due prior to maturity.