Preferred Stock (Details) (USD $)	9 Months Ended	0 Months Ended			1 Months Ended	9 Months Ended	0 Months Ended				9 Months Ended	0 Months Ended
	Sep. 30, 2013	Jul. 07, 2014 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Apr. 09, 2014 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Jan. 07, 2014 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Feb. 21, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Sep. 30, 2014 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Jul. 07, 2014 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Apr. 09, 2014 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Jan. 07, 2014 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Aug. 01, 2013 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Sep. 30, 2014 Series B Cumulative Redeemable Perpetual Preferred Stock [Member]	Oct. 06, 2014 Subsequent Event [Member] Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Oct. 06, 2014 Subsequent Event [Member] 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	$ 2.375			$ 2.25	$ 2.25	$ 2.25			$ 2.375	$ 2.25
Accumulated unpaid dividends						$ 0					$ 0
Preferred stock, redemption date						Apr. 30, 2018					Oct. 30, 2018
Cash redemption price (in dollars 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