Credit Facility (Details) (Subsequent Event [Member], Unsecured Revolving Credit Facility [Member], USD $)	0 Months Ended
	Jan. 07, 2015	Jan. 07, 2015
Line of Credit Facility [Line Items]
Potential increase in revolving credit facility commitment	$ 250,000,000	$ 250,000,000
Bank of America, N.A. [Member]
Line of Credit Facility [Line Items]
Unsecured credit facility maximum amount	250,000,000	250,000,000
Credit facility term	5 years
Line of Credit Facility, Amount Outstanding	$ 95,000,000	$ 95,000,000
Consolidated leverage ratio (note more than)	3.5
Consolidated interest coverage ratio (not less than)	3.0