Equity and Capital (Details) (USD $)	3 Months Ended		13 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 01, 2013
Targeted or Tracking Stock, Stock [Line Items]
Common stock offering, maximum aggregate price				$ 300,000,000
Commission to sales agent, maximum (percent)				2.00%
Net proceeds	35,000	43,869,000
Stock issued during period, new issues (in shares)	238,693	2,096,655	8,419,298.000
Common stock offering, maximum aggregate price still available	88,507,000		88,507,000
At The Market Stock Sales [Member]
Targeted or Tracking Stock, Stock [Line Items]
Number of shares settled		1,889,105
Gross proceeds		44,459,000
Net proceeds		$ 43,904,000
Weighted-average sales price		$ 23.53