Represents the number of shares permitted to be issued under the equity offering plan.

No definition available.

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- Definition

Represents the number of new preferred stock shares issued during the period.

+ References

No definition available.

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- Definition

The total fair value of equity-based payment equity instruments, excluding stock or unit options, as of grant date.

+ References

No definition available.

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Represents the amount of securities for which the entity filed shelf registration statement on Form S-3 with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the 1933 Act).

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No definition available.

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- Definition

Represents the amount of shares for which the entity filed shelf registration statement on Form S-3 with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the 1933 Act) that are currently available under shelf registration.

+ References

No definition available.

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- Definition

Number of new stock issued during the period on exercise of over-allotment option by underwriters.

+ References

No definition available.

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- Definition

Equity impact of the value of new stock issued during the period on exercise of over-allotment option by underwriters.

+ References

No definition available.

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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-Name Staff Accounting Bulletin (SAB)

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

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Aggregate dividends declared during the period for each share of preferred stock outstanding.

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No definition available.

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- Definition

The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

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-Subparagraph (SX 210.4-08.(d)(1))

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- Definition

The cash inflow from the additional capital contribution to the entity.

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

+ References

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- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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No definition available.

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- Definition

Percentage of vesting of share-based compensation awards.

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

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Number of new stock issued during the period.

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-Name Regulation S-X (SX)

-Number 210

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Gross number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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No definition available.

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Equity (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended		1 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended	9 Months Ended		12 Months Ended	9 Months Ended	0 Months Ended			1 Months Ended	0 Months Ended				1 Months Ended	0 Months Ended			1 Months Ended	9 Months Ended	0 Months Ended				1 Months Ended		3 Months Ended	8 Months Ended	9 Months Ended			0 Months Ended	1 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
Equity (Details) (USD $)	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Nov. 07, 2014	Sep. 30, 2014 Non-employees ACM Restricted common stock	Sep. 30, 2014 Non-employees ACM Selling and administrative expense Restricted common stock	Sep. 30, 2013 Non-employees ACM Selling and administrative expense Restricted common stock	Sep. 30, 2014 Non-employees ACM Selling and administrative expense Restricted common stock	Sep. 30, 2013 Non-employees ACM Selling and administrative expense Restricted common stock	Sep. 30, 2014 Employees Restricted common stock	Sep. 30, 2014 Employees Employee compensation and benefits Restricted common stock	Sep. 30, 2013 Employees Employee compensation and benefits Restricted common stock	Sep. 30, 2014 Employees Employee compensation and benefits Restricted common stock	Sep. 30, 2013 Employees Employee compensation and benefits Restricted common stock	May 31, 2014 Employees of the company and a related party ACM Restricted common stock	Sep. 30, 2014 Employees of the company and a related party ACM Restricted common stock May, 2015	Sep. 30, 2014 Employees of the company and a related party ACM Restricted common stock May, 2016	Jun. 30, 2014 Employees of the company and a related party ACM Employee compensation and benefits Restricted common stock	Jun. 30, 2014 Employees of the company and a related party ACM Selling and administrative expense Restricted common stock	Sep. 30, 2014 8.25% Series A cumulative redeemable preferred stock	Sep. 30, 2013 8.25% Series A cumulative redeemable preferred stock	Dec. 31, 2013 8.25% Series A cumulative redeemable preferred stock	Sep. 30, 2014 7.75% Series B cumulative redeemable preferred stock	Sep. 30, 2013 7.75% Series B cumulative redeemable preferred stock	Dec. 31, 2013 7.75% Series B cumulative redeemable preferred stock	Sep. 30, 2014 8.50% Series C preferred stock	Jul. 30, 2014 Preferred Stock 8.25% Series A cumulative redeemable preferred stock	Apr. 29, 2014 Preferred Stock 8.25% Series A cumulative redeemable preferred stock	Feb. 03, 2014 Preferred Stock 8.25% Series A cumulative redeemable preferred stock	Feb. 28, 2013 Preferred Stock 8.25% Series A cumulative redeemable preferred stock	Oct. 31, 2014 Preferred Stock 8.25% Series A cumulative redeemable preferred stock Subsequent event	Jul. 30, 2014 Preferred Stock 7.75% Series B cumulative redeemable preferred stock	Apr. 29, 2014 Preferred Stock 7.75% Series B cumulative redeemable preferred stock	Feb. 03, 2014 Preferred Stock 7.75% Series B cumulative redeemable preferred stock	May 31, 2013 Preferred Stock 7.75% Series B cumulative redeemable preferred stock	Oct. 31, 2014 Preferred Stock 7.75% Series B cumulative redeemable preferred stock Subsequent event	Jul. 30, 2014 Preferred Stock 8.50% Series C preferred stock	Apr. 29, 2014 Preferred Stock 8.50% Series C preferred stock	Feb. 28, 2014 Preferred Stock 8.50% Series C preferred stock	Sep. 30, 2014 Preferred Stock 8.50% Series C preferred stock	Oct. 31, 2014 Preferred Stock 8.50% Series C preferred stock Subsequent event	Jul. 30, 2014 Common Stock	Apr. 29, 2014 Common Stock	Feb. 12, 2014 Common Stock	Sep. 30, 2013 Common Stock	Mar. 31, 2013 Common Stock	Mar. 31, 2013 Common Stock	Sep. 30, 2014 Common Stock	Sep. 30, 2014 Common Stock	Feb. 28, 2014 Common Stock	Dec. 31, 2012 Common Stock	Nov. 05, 2014 Common Stock Subsequent event	May 31, 2014 Common Stock Non-management members of the Board of Directors	Sep. 30, 2013 Common Stock Non-management members of the Board of Directors Employee compensation and benefits	Jun. 30, 2014 Common Stock Non-management members of the Board of Directors Selling and administrative expense	Sep. 30, 2013 Common Stock Non-management members of the Board of Directors Selling and administrative expense
Preferred Stock
Issuance of preferred stock (in shares)																															1,400,000					1,200,000				900,000	900,000
Return on the preferred shares issued to third parties by its subsidiary REIT (as a percent)																					8.25%	8.25%	8.25%	7.75%	7.75%	7.75%	8.50%				8.25%	8.25%				7.75%	7.75%			8.50%		8.50%
Preferred stock, liquidation preference (in dollars per share)																															$ 25.00					$ 25.00				$ 25.00
Net proceeds from issuance of preferred stock			$ 22,500,000	$ 70,287,500																											$ 33,600,000					$ 28,900,000				$ 21,600,000
Option exercised by underwriters (in shares)																															151,500					60,000
Additional net proceeds from exercise of option by underwriters																															3,700,000					1,500,000
Common stock
Issuance of common stock (in shares)																																														6,000,000	5,625,000	6,000,000	1,000,000	1,000,000
Value of common shares issued to the public (in dollars per share)																																														$ 7.08	$ 8.00	$ 8.00
Proceeds from issuance of shares under public offering			6,800,000	134,176,328																																										40,900,000	43,000,000	45,600,000	6,500,000
Number of shares which the entity may issue and sell through JMP																																																			7,500,000	6,000,000
Value of common stock remaining under shelf registration					330,400,000
Aggregate amount of securities for which the entity filed shelf registration statement					500,000,000
Distributions
Cash dividend declared (in dollars per share)	$ 0.13	$ 0.13	$ 0.39	$ 0.37																																							$ 0.13	$ 0.13	$ 0.13								$ 0.13
Cash dividend declared on redeemable preferred stock (in dollars per share)																												$ 0.515625	$ 0.515625	$ 0.515625		$ 0.515625	$ 0.484375	$ 0.484375	$ 0.484375		$ 0.484375	$ 0.53125	$ 0.5549			$ 0.53125
Deferred Compensation
Granted (in shares)						138,584					110,666
Total grant date fair value						1,000,000					800,000					2,000,000
Share-based compensation expense							$ 200,000	$ 100,000	$ 300,000	$ 200,000		$ 100,000	$ 100,000	$ 300,000	$ 200,000				$ 300,000	$ 300,000																																			$ 200,000	$ 400,000	$ 900,000
Number of fully vested shares issued																278,000																																						63,000
Vesting percentage																33.00%	33.00%	33.00%