Restated Consolidated Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (301,566)	[1],[2]
Adjustments to reconcile net loss to net cash provided by operating activities:
Issuance of operating partnership units for ARCT III Merger and other transaction related expenses	107,771	[1]
Depreciation	131,605	[1]
(Gain) loss on held for sale properties	0	[1]
Impairment of real estate	2,074	[1]	3,300
Equity-based compensation	13,981	[1]
Loss on derivative instruments	144	[1]
Unrealized loss on investments	14	[1]
Unrealized loss on contingent value rights obligations, net of settlement payments	49,314	[1]
Convertible obligations to Series C Convertible Preferred stockholders, fair value adjustment	4,827	[1]
(Gain) loss on sale of investments	1,795	[1]
Changes in assets and liabilities:
Investment in direct financing leases	148	[1]
Prepaid expenses and other assets	(20,513)	[1]
Accounts payable and accrued expenses	10,435	[1]
Deferred rent and other liabilities	5,911	[1]
Due from affiliates	(4,105)	[1]
Due to affiliates	6,107
Net cash provided by (used in) operating activities	7,942	[1]
Cash flows from investing activities:
Investments in real estate and other assets	(3,241,834)	[1]
Investment in direct financing leases	(75,551)	[1]
Capital expenditures	(113)	[1]
Purchase of assets from Manager	0
Deposits for real estate investments	(31,115)	[1]
Purchases of investment securities	(81,464)	[1]
Proceeds from sale of investment securities	111,402	[1]
Net cash used in investing activities	(3,318,675)	[1]
Cash flows from financing activities:
Proceeds from mortgage notes payable	6,897	[1]
Proceeds from senior corporate credit facility	1,570,000
Payments on senior corporate credit facility	(384,604)
Proceeds from corporate bonds	(53,397)	[1]
Proceeds from issuance of convertible debt	310,000	[1]
Common stock repurchases	(358,093)	[1]
Proceeds from issuance of convertible obligations to Series C Convertible Preferred stockholders	445,000
Proceeds from issuance of common stock, net	1,807,197	[1]
Payments of deferred financing costs	(2,165)	[1]
Consideration paid for assets of Manager in excess of carryover basis	0
Contributions from non-controlling interest holders	29,758	[1]
Distributions to non-controlling interest holders	(5,615)	[1]
Distributions paid	(157,646)	[1]
Advances from affiliates, net	(376)
Restricted cash	(572)	[1]
Net cash provided by financing activities	3,206,384	[1]
Net change in cash and cash equivalents	(104,349)	[1]
Cash and cash equivalents, beginning of period	292,575	[1]	292,575	[1]
Cash and cash equivalents, end of period	188,226	[1]	52,725	[1]
As Previously Reported [Member]
Cash flows from operating activities:
Net loss	(249,393)	[3],[4]
Adjustments to reconcile net loss to net cash provided by operating activities:
Issuance of operating partnership units for ARCT III Merger and other transaction related expenses	108,247	[4]
Depreciation	99,832	[4]
(Gain) loss on held for sale properties	(14)	[4]
Impairment of real estate	0	[3],[4]
Equity-based compensation	13,895	[4]
Loss on derivative instruments	144	[4]
Unrealized loss on investments	14	[4]
Unrealized loss on contingent value rights obligations, net of settlement payments	49,314	[4]
Convertible obligations to Series C Convertible Preferred stockholders, fair value adjustment	4,827	[4]
(Gain) loss on sale of investments	(451)	[3],[4]
Changes in assets and liabilities:
Investment in direct financing leases	102	[4]
Prepaid expenses and other assets	(12,081)	[4]
Accounts payable and accrued expenses	4,464	[4]
Deferred rent and other liabilities	3,068	[4]
Due from affiliates	0	[4]
Due to affiliates	0	[4]
Net cash provided by (used in) operating activities	21,968	[4]
Cash flows from investing activities:
Investments in real estate and other assets	(1,173,497)	[4]
Investment in direct financing leases	(57,551)	[4]
Capital expenditures	(113)	[4]
Purchase of assets from Manager	(1,041)	[4]
Deposits for real estate investments	(28,836)	[4]
Purchases of investment securities	(12,004)	[4]
Proceeds from sale of investment securities	44,188	[4]
Net cash used in investing activities	(1,228,854)	[4]
Cash flows from financing activities:
Proceeds from mortgage notes payable	4,773	[4]
Proceeds from senior corporate credit facility	860,000	[4]
Payments on senior corporate credit facility	(384,604)	[4]
Proceeds from corporate bonds	(38,221)	[4]
Proceeds from issuance of convertible debt	310,000	[4]
Common stock repurchases	(357,916)	[4]
Proceeds from issuance of convertible obligations to Series C Convertible Preferred stockholders	445,000	[4]
Proceeds from issuance of common stock, net	486,536	[4]
Payments of deferred financing costs	0	[4]
Consideration paid for assets of Manager in excess of carryover basis	(3,035)	[4]
Contributions from non-controlling interest holders	750	[4]
Distributions to non-controlling interest holders	(5,170)	[4]
Distributions paid	(117,047)	[4]
Advances from affiliates, net	0	[4]
Restricted cash	(572)	[4]
Net cash provided by financing activities	1,200,494	[4]
Net change in cash and cash equivalents	(6,392)	[4]
Cash and cash equivalents, beginning of period	156,873	[4]	156,873	[4]
Cash and cash equivalents, end of period	150,481	[3],[4]
Reclassifications And Immaterial Adjustments [Member]
Cash flows from operating activities:
Net loss	0
Adjustments to reconcile net loss to net cash provided by operating activities:
Impairment of real estate	0
(Gain) loss on sale of investments	0
Cash flows from financing activities:
Cash and cash equivalents, end of period	0
Reclassifications And Immaterial Adjustments [Member] | ARCT IV [Member]
Cash flows from operating activities:
Net loss	(47,551)	[5]
Adjustments to reconcile net loss to net cash provided by operating activities:
Issuance of operating partnership units for ARCT III Merger and other transaction related expenses	0	[5]
Depreciation	31,501	[5]
(Gain) loss on held for sale properties	0	[5]
Impairment of real estate	0	[5]
Equity-based compensation	18	[5]
Loss on derivative instruments	0	[5]
Unrealized loss on investments	0	[5]
Unrealized loss on contingent value rights obligations, net of settlement payments	0	[5]
Convertible obligations to Series C Convertible Preferred stockholders, fair value adjustment	0	[5]
(Gain) loss on sale of investments	2,246	[5]
Changes in assets and liabilities:
Investment in direct financing leases	46	[5]
Prepaid expenses and other assets	(8,432)	[5]
Accounts payable and accrued expenses	11,251	[5]
Deferred rent and other liabilities	2,843	[5]
Due from affiliates	(4,105)	[5]
Due to affiliates	0	[5]
Net cash provided by (used in) operating activities	(12,183)	[5]
Cash flows from investing activities:
Investments in real estate and other assets	(2,068,337)	[5]
Investment in direct financing leases	(18,000)	[5]
Capital expenditures	0	[5]
Purchase of assets from Manager	0	[5]
Deposits for real estate investments	(2,279)	[5]
Purchases of investment securities	(69,460)	[5]
Proceeds from sale of investment securities	67,214	[5]
Net cash used in investing activities	(2,090,862)	[5]
Cash flows from financing activities:
Proceeds from mortgage notes payable	2,124	[5]
Proceeds from senior corporate credit facility	710,000	[5]
Payments on senior corporate credit facility	0	[5]
Proceeds from corporate bonds	(15,176)	[5]
Proceeds from issuance of convertible debt	0	[5]
Common stock repurchases	(177)	[5]
Proceeds from issuance of convertible obligations to Series C Convertible Preferred stockholders	0	[5]
Proceeds from issuance of common stock, net	1,320,729	[5]
Payments of deferred financing costs	0	[5]
Consideration paid for assets of Manager in excess of carryover basis	0	[5]
Contributions from non-controlling interest holders	29,008	[5]
Distributions to non-controlling interest holders	(445)	[5]
Distributions paid	(40,599)	[5]
Advances from affiliates, net	(376)	[5]
Restricted cash	0	[5]
Net cash provided by financing activities	2,005,088	[5]
Net change in cash and cash equivalents	(97,957)	[5]
Cash and cash equivalents, beginning of period	135,702	[5]	135,702	[5]
Cash and cash equivalents, end of period	37,745	[5]
Error Corrections [Member]
Cash flows from operating activities:
Net loss	(4,622)
Adjustments to reconcile net loss to net cash provided by operating activities:
Issuance of operating partnership units for ARCT III Merger and other transaction related expenses	(476)
Depreciation	272
(Gain) loss on held for sale properties	14
Impairment of real estate	2,074
Equity-based compensation	68
Loss on derivative instruments	0
Unrealized loss on investments	0
Unrealized loss on contingent value rights obligations, net of settlement payments	0
Convertible obligations to Series C Convertible Preferred stockholders, fair value adjustment	0
(Gain) loss on sale of investments	0
Changes in assets and liabilities:
Investment in direct financing leases	0
Prepaid expenses and other assets	0
Accounts payable and accrued expenses	(5,280)
Deferred rent and other liabilities	0
Due from affiliates	0
Due to affiliates	6,107
Net cash provided by (used in) operating activities	(1,843)
Cash flows from investing activities:
Investments in real estate and other assets	0
Investment in direct financing leases	0
Capital expenditures	0
Purchase of assets from Manager	1,041
Deposits for real estate investments	0
Purchases of investment securities	0
Proceeds from sale of investment securities	0
Net cash used in investing activities	1,041
Cash flows from financing activities:
Proceeds from mortgage notes payable	0
Proceeds from senior corporate credit facility	0
Payments on senior corporate credit facility	0
Proceeds from corporate bonds	0
Proceeds from issuance of convertible debt	0
Common stock repurchases	0
Proceeds from issuance of convertible obligations to Series C Convertible Preferred stockholders	0
Proceeds from issuance of common stock, net	(68)
Payments of deferred financing costs	(2,165)
Consideration paid for assets of Manager in excess of carryover basis	3,035
Contributions from non-controlling interest holders	0
Distributions to non-controlling interest holders	0
Distributions paid	0
Advances from affiliates, net	0
Restricted cash	0
Net cash provided by financing activities	802
Net change in cash and cash equivalents	0
Cash and cash equivalents, beginning of period	0		0
Cash and cash equivalents, end of period	$ 0

[1] For discussion on the restatement adjustments, see Note 2 - Restatement of Previously Issued Consolidated Financial Statements.

[2] For discussion of the restatement adjustments, see Note 2 - Restatement of Previously Issued Consolidated Financial Statements.

[3] Certain line items have been consolidated from the original presentation in the Quarterly Report on Form 10-Q filing for the three and nine month period ended September 30, 2013.

[4] Certain line items have been consolidated from the original presentation in the Quarterly Report on Form 10-Q filing for the nine month period ended September 30, 2013.

[5] These financial statements have been recast in applying the carryover basis of accounting to include ARCT IV.