Net Loss Per Share (Schedule of Earnings Per Share, Basic and Diluted)(Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended			12 Months Ended		3 Months Ended				3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012	Dec. 31, 2012		Mar. 31, 2013 Restricted Unvested Common Stock [Member]	Mar. 31, 2013 Class A Units [Member] [Member]	Mar. 31, 2013 Class B Units [Member]	Feb. 28, 2013 Cash [Member] Option Two [Member] ARCP shares converted from ARCT III shares [Member]	Mar. 31, 2013 Excluding Pro Forma Adjustment [Domain]
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Shares, Outstanding									27,700,000
Net loss from continuing operations attributable to stockholders	$ (137,918)		$ (4,706)	$ (4,706)
Less: dividends declared on Preferred shares	(158)			0
Net Income (Loss) Before Discontinued operations After Adjustments for Dividends on Preferred Stock, Available to Common Stockholders, Basic	(138,076)			(4,706)
Net loss from discontinued operations attributable to stockholders	(2)		(322)	(322)
Net loss from continuing operations attributable to common stockholders	$ (138,078)			$ (5,028)
Weighted average common shares outstanding	153,339,174	[1]		23,609,509	[1]					171,049,690
Basic and diluted net loss per share from continuing operations attributable to common stockholders	$ (0.90)			$ (0.20)
Basic and diluted net loss per share from discontinued operations attributable to stockholders	$ 0.00			$ (0.01)
Basic and diluted net loss per share attributable to common stockholders	$ (0.90)			$ (0.21)						$ (0.81)
Antidilutive securtities excluded from computation of earnings per share	9,650,894					331,000	545,454	283,018

[1] Weighted average shares are adjusted on a pro forma basis as if the purchase of 27.7 million shares of ARCT III common stock for cash, purchased in conjunction with the Merger, had been completed at the beginning of the period. Weighted average shares excluding this pro forma adjustment was 171,049,690 and net loss per share was $(0.81) per share, basic and diluted.