Preferred Stock (Details) (USD $)	9 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended	9 Months Ended	0 Months Ended		9 Months Ended
	Sep. 30, 2013	Oct. 08, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Jul. 17, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Apr. 10, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Feb. 21, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Sep. 30, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Oct. 08, 2013 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Aug. 01, 2013 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Sep. 30, 2013 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock issued					250,000			316,250
Preferred stock, dividend rate					9.50%			9.00%
Preferred stock, par value					$ 1.00			$ 1.00
Preferred stock, liquidation preference per share					$ 100.00			$ 100.00
Shares sold pursuant to over-allotment option granted to underwriters for offering								41,250
Preferred stock, dividend declared		$ 2.375	$ 2.375	$ 1.79			$ 2.25
Preferred stock, redemption date						Apr. 30, 2018			Oct. 30, 2018
Preferred stock, cash redemption price per share						$ 100.00			$ 100.00
Net proceeds from the issuance of preferred stock	$ 53,336,000					$ 23,400,000			$ 30,000,000
Underwriter discounts and related costs						$ 1,600,000			$ 1,600,000
Period after change of control to redeem shares						120 days			120 days