Condensed Consolidating Financial Information - Condensed Consolidated Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating Activities
Net cash provided by (used in) operating activities	$ 101,564	$ 74,709
Investing activities
Cash paid for acquisitions and other related investments	(371,500)	(606,500)
Principal received on loans receivable	4,694	9,507
Net proceeds from sale of real estate	18,409
Net proceeds from sale of real estate	18,409	34,100
Investments in loans receivable	(1,445)	(1,293)
Construction in progress and other	(63,422)	(35,920)
Net cash provided by (used in) investing activities	(413,264)	(600,106)
Financing Activities
Revolving credit facilities, net	(80,000)	35,400
Additions to term debt	153,000	300,000
Payments of term debt	(11,185)	(171)
Distributions paid	(87,928)	(76,770)
Proceeds from sale of common shares/units, net of offering costs	313,319	220,107
Lease deposits and other obligations to tenants	3,589	(13,391)
Debt issuance costs paid and other financing activities	(4,282)	(6,341)
Net cash provided by (used in) financing activities	286,513	458,834
Increase (decrease) in cash and cash equivalents for period	(25,187)	(66,563)
Cash and cash equivalents at beginning of period	37,311	102,726
Cash and cash equivalents at end of period	12,124	36,163
Parent
Operating Activities
Net cash provided by (used in) operating activities	91	16
Investing activities
Investments in and advances to subsidiaries	(225,683)	(143,554)
Net cash provided by (used in) investing activities	(225,683)	(143,554)
Financing Activities
Distributions paid	(87,727)	(76,569)
Proceeds from sale of common shares/units, net of offering costs	313,319	220,107
Net cash provided by (used in) financing activities	225,592	143,538
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
Subsidiary Issuers
Operating Activities
Net cash provided by (used in) operating activities	(38,891)	(38,780)
Investing activities
Investments in and advances to subsidiaries	(267,545)	(540,016)
Construction in progress and other	(765)	(59)
Net cash provided by (used in) investing activities	(268,310)	(540,075)
Financing Activities
Revolving credit facilities, net	(80,000)	75,000
Additions to term debt	153,000	300,000
Payments of term debt	(11,000)
Distributions paid	(87,928)	(76,770)
Proceeds from sale of common shares/units, net of offering costs	313,319	220,107
Debt issuance costs paid and other financing activities	(4,282)	(6,341)
Net cash provided by (used in) financing activities	283,109	511,996
Increase (decrease) in cash and cash equivalents for period	(24,092)	(66,859)
Cash and cash equivalents at beginning of period	35,483	101,230
Cash and cash equivalents at end of period	11,391	34,371
Subsidiary Guarantors
Operating Activities
Net cash provided by (used in) operating activities	156,913	109,018
Investing activities
Cash paid for acquisitions and other related investments	(95,000)	(410,000)
Principal received on loans receivable		5,491
Net proceeds from sale of real estate		800
Investments in and advances to subsidiaries	(1,506)	380,605
Construction in progress and other	(63,691)	(33,869)
Net cash provided by (used in) investing activities	(160,197)	(56,973)
Financing Activities
Revolving credit facilities, net		(39,600)
Lease deposits and other obligations to tenants	1,719	(12,289)
Net cash provided by (used in) financing activities	1,719	(51,889)
Increase (decrease) in cash and cash equivalents for period	(1,565)	156
Cash and cash equivalents at beginning of period	1,565	1,409
Cash and cash equivalents at end of period		1,565
Non-Guarantor Subsidiaries
Operating Activities
Net cash provided by (used in) operating activities	(16,549)	4,455
Investing activities
Cash paid for acquisitions and other related investments	(276,500)	(196,500)
Principal received on loans receivable	4,694	4,016
Net proceeds from sale of real estate	18,409
Net proceeds from sale of real estate		33,300
Investments in and advances to subsidiaries	269,142	159,427
Investments in loans receivable	(1,445)	(1,293)
Construction in progress and other	1,034	(1,992)
Net cash provided by (used in) investing activities	15,334	(3,042)
Financing Activities
Payments of term debt	(185)	(171)
Lease deposits and other obligations to tenants	1,870	(1,102)
Net cash provided by (used in) financing activities	1,685	(1,273)
Increase (decrease) in cash and cash equivalents for period	470	140
Cash and cash equivalents at beginning of period	263	87
Cash and cash equivalents at end of period	733	227
Eliminations
Investing activities
Investments in and advances to subsidiaries	225,592	143,538
Net cash provided by (used in) investing activities	225,592	143,538
Financing Activities
Distributions paid	87,727	76,569
Proceeds from sale of common shares/units, net of offering costs	(313,319)	(220,107)
Net cash provided by (used in) financing activities	(225,592)	(143,538)
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period