Condensed Consolidated Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating Activities
Net cash provided by (used in) operating activities	$ 44,423	$ 39,692
Investing Activities
Principal received on loans receivable	7,966	1,469
Proceeds from sales of real estate	16,000
Investments in loans receivable	(1,293)	(229)
Construction in progress and other	(20,655)	(7,976)
Net cash provided by (used in) investing activities	(394,482)	(186,723)
Financing activities
Revolving credit facilities, net	(89,600)	39,600
Additions to term debt	300,000	450,000
Payments of term debt	(114)	(157,736)
Distributions paid	(49,589)	(44,784)
Sale of common stock, net	220,160
Lease deposits and other obligations to tenants	383	4,328
Debt issuance costs paid and other financing activities	(6,268)	(14,879)
Net cash provided by (used in) financing activities	374,972	276,529
Increase (decrease) in cash and cash equivalents for period	24,913	129,498
Cash and cash equivalents at beginning of period	102,726	98,408
Cash and cash equivalents at end of period	127,639	227,906
Parent
Operating Activities
Net cash provided by (used in) operating activities		(158)
Investing Activities
Investments in and advances to subsidiaries	(170,705)	44,818
Net cash provided by (used in) investing activities	(170,705)	44,818
Financing activities
Distributions paid	(49,455)	(44,660)
Sale of common stock, net	220,160
Net cash provided by (used in) financing activities	170,705	(44,660)
Subsidiary Issuers
Operating Activities
Net cash provided by (used in) operating activities	(30,512)	(19,700)
Investing Activities
Investments in and advances to subsidiaries	(359,319)	(90,945)
Construction in progress and other	(47)	(112)
Net cash provided by (used in) investing activities	(359,366)	(91,057)
Financing activities
Revolving credit facilities, net	(50,000)
Additions to term debt	300,000	450,000
Payments of term debt		(149,250)
Distributions paid	(49,589)	(44,784)
Sale of common stock, net	220,160
Debt issuance costs paid and other financing activities	(6,268)	(14,743)
Net cash provided by (used in) financing activities	414,303	241,223
Increase (decrease) in cash and cash equivalents for period	24,425	130,466
Cash and cash equivalents at beginning of period	101,230	96,822
Cash and cash equivalents at end of period	125,655	227,288
Subsidiary Guarantors
Operating Activities
Net cash provided by (used in) operating activities	75,358	54,877
Investing Activities
Cash paid for acquisitions and other related investments	(200,000)	(168,600)
Principal received on loans receivable	5,491
Investments in and advances to subsidiaries	179,010	83,887
Construction in progress and other	(19,970)	(7,368)
Net cash provided by (used in) investing activities	(35,469)	(92,081)
Financing activities
Revolving credit facilities, net	(39,600)	39,600
Payments of term debt		(8,443)
Lease deposits and other obligations to tenants	(133)	5,127
Net cash provided by (used in) financing activities	(39,733)	36,294
Increase (decrease) in cash and cash equivalents for period	156	(910)
Cash and cash equivalents at beginning of period	1,409	1,387
Cash and cash equivalents at end of period	1,565	477
Non-Guarantor Subsidiaries
Operating Activities
Net cash provided by (used in) operating activities	(423)	4,673
Investing Activities
Cash paid for acquisitions and other related investments	(196,500)	(11,387)
Principal received on loans receivable	2,475	1,469
Proceeds from sales of real estate	16,000
Investments in and advances to subsidiaries	180,309	6,900
Investments in loans receivable	(1,293)	(229)
Construction in progress and other	(638)	(496)
Net cash provided by (used in) investing activities	353	(3,743)
Financing activities
Payments of term debt	(114)	53
Lease deposits and other obligations to tenants	516	(799)
Debt issuance costs paid and other financing activities		(136)
Net cash provided by (used in) financing activities	402	(988)
Increase (decrease) in cash and cash equivalents for period	332	(58)
Cash and cash equivalents at beginning of period	87	199
Cash and cash equivalents at end of period	419	141
Eliminations
Investing Activities
Investments in and advances to subsidiaries	170,705	(44,660)
Net cash provided by (used in) investing activities	170,705	(44,660)
Financing activities
Distributions paid	49,455	44,660
Sale of common stock, net	(220,160)
Net cash provided by (used in) financing activities	(170,705)	44,660
Total Consolidated
Operating Activities
Net cash provided by (used in) operating activities	44,423	39,692
Investing Activities
Cash paid for acquisitions and other related investments	(396,500)	(179,987)
Principal received on loans receivable	7,966	1,469
Proceeds from sales of real estate	16,000
Investments in loans receivable	(1,293)	(229)
Construction in progress and other	(20,655)	(7,976)
Net cash provided by (used in) investing activities	(394,482)	(186,723)
Financing activities
Revolving credit facilities, net	(89,600)	39,600
Additions to term debt	300,000	450,000
Payments of term debt	(114)	(157,736)
Distributions paid	(49,589)	(44,784)
Sale of common stock, net	220,160
Lease deposits and other obligations to tenants	383	4,328
Debt issuance costs paid and other financing activities	(6,268)	(14,879)
Net cash provided by (used in) financing activities	374,972	276,529
Increase (decrease) in cash and cash equivalents for period	24,913	129,498
Cash and cash equivalents at beginning of period	102,726	98,408
Cash and cash equivalents at end of period	$ 127,639	$ 227,906