Preferred Stock (Details) (USD $)	12 Months Ended	0 Months Ended					12 Months Ended	0 Months Ended			12 Months Ended
	Dec. 31, 2013	Jan. 07, 2014 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	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]	Dec. 31, 2013 Series A Cumulative Redeemable Perpetual Preferred Stock [Member]	Jan. 07, 2014 Series B 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]	Dec. 31, 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	$ 2.375	$ 1.79			$ 2.25	$ 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	53,333,000						23,400,000				30,000,000
Underwriter discounts and related costs							$ 1,600,000				$ 1,700,000
Period after change of control to redeem shares							120 days				120 days