Guarantor and Non-Guarantor Financial Information - Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By/(Used In) Operating Activities	$ 235,809	$ 219,044	$ 217,158
Cash Flows from Investing Activities:
Investment in real estate assets, consolidated joint venture, and real estate related intangibles, net of accruals	(459,896)	(501,444)	(291,459)
Intercompany note receivable	0	0	0
Redemption of noncontrolling interest in unconsolidated variable interest entity	0	(4,000)	0
Net sale proceeds from wholly-owned properties	365,918	848,169	46,232
Net sale proceeds received from unconsolidated joint ventures	0	0	6,017
Investments in unconsolidated joint ventures	0	0	(42)
Deferred lease costs paid	(25,896)	(37,683)	(27,694)
Net cash provided by/(used in) investing activities	(119,874)	305,042	(266,946)
Cash Flows from Financing Activities:
Debt issuance costs paid	(264)	(1,081)	(1,294)
Proceeds from debt	695,000	1,301,858	1,052,527
Repayments of debt	(706,875)	(1,544,301)	(813,702)
Discount due to loan modification	0	0	(1,135)
Intercompany note payable	0	0	0
Costs of issuance of common stock	(342)	(326)	0
Shares withheld to pay tax obligations related to employee stock compensation	(2,344)	(1,710)	(1,275)
Repurchases of common stock as part of announced plan	(7,943)	(158,860)	(54,802)
(Distributions to)/repayments from affiliates	0	0	0
Dividends paid and discount on dividend reinvestments	(91,616)	(126,531)	(125,198)
Net cash provided by/(used in) financing activities	(114,384)	(530,951)	55,121
Net increase/(decrease) in cash and cash equivalents	1,551	(6,865)	5,333
Cash and cash equivalents, beginning of year	5,441	12,306	6,973
Cash and cash equivalents, end of year	6,992	5,441	12,306
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By/(Used In) Operating Activities	35,660	36,245	28,733
Cash Flows from Investing Activities:
Investment in real estate assets, consolidated joint venture, and real estate related intangibles, net of accruals	0	0	0
Intercompany note receivable	71,460	(72,000)	(650)
Redemption of noncontrolling interest in unconsolidated variable interest entity		0
Net sale proceeds from wholly-owned properties	0	0	0
Net sale proceeds received from unconsolidated joint ventures			0
Investments in unconsolidated joint ventures			0
Deferred lease costs paid	0	0	0
Net cash provided by/(used in) investing activities	71,460	(72,000)	(650)
Cash Flows from Financing Activities:
Debt issuance costs paid	0	0	0
Proceeds from debt	0	0	0
Repayments of debt	0	0	0
Discount due to loan modification			0
Intercompany note payable	(71,460)	72,000	650
Costs of issuance of common stock	0	0
Shares withheld to pay tax obligations related to employee stock compensation	0	0
Repurchases of common stock as part of announced plan	0	0	0
(Distributions to)/repayments from affiliates	(35,660)	(36,245)	(28,733)
Dividends paid and discount on dividend reinvestments	0	0	0
Net cash provided by/(used in) financing activities	(107,120)	35,755	(28,083)
Net increase/(decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents, beginning of year	0	0	0
Cash and cash equivalents, end of year	0	0	0
Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By/(Used In) Operating Activities	(26,260)	(27,077)	5,448
Cash Flows from Investing Activities:
Investment in real estate assets, consolidated joint venture, and real estate related intangibles, net of accruals	(5,060)	(12,203)	(23,541)
Intercompany note receivable	440	72,000	650
Redemption of noncontrolling interest in unconsolidated variable interest entity		0
Net sale proceeds from wholly-owned properties	200,220	151,557	29,519
Net sale proceeds received from unconsolidated joint ventures			6,017
Investments in unconsolidated joint ventures			(42)
Deferred lease costs paid	(2,758)	(3,792)	(4,472)
Net cash provided by/(used in) investing activities	192,842	207,562	8,131
Cash Flows from Financing Activities:
Debt issuance costs paid	(264)	(575)	(1,294)
Proceeds from debt	695,000	1,142,577	1,052,527
Repayments of debt	(538,000)	(1,438,000)	(238,000)
Discount due to loan modification			(1,135)
Intercompany note payable	(9,600)	0	0
Costs of issuance of common stock	0	0
Shares withheld to pay tax obligations related to employee stock compensation	0	0	0
Repurchases of common stock as part of announced plan	0	0	0
(Distributions to)/repayments from affiliates	(312,218)	109,544	(820,795)
Dividends paid and discount on dividend reinvestments	0	0	0
Net cash provided by/(used in) financing activities	(165,082)	(186,454)	(8,697)
Net increase/(decrease) in cash and cash equivalents	1,500	(5,969)	4,882
Cash and cash equivalents, beginning of year	2,174	8,143	3,261
Cash and cash equivalents, end of year	3,674	2,174	8,143
Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By/(Used In) Operating Activities	5,214	4,699	4,088
Cash Flows from Investing Activities:
Investment in real estate assets, consolidated joint venture, and real estate related intangibles, net of accruals	0	0	0
Intercompany note receivable	0	0	0
Redemption of noncontrolling interest in unconsolidated variable interest entity		0
Net sale proceeds from wholly-owned properties	0	0	0
Net sale proceeds received from unconsolidated joint ventures			0
Investments in unconsolidated joint ventures			0
Deferred lease costs paid	0	0	0
Net cash provided by/(used in) investing activities	0	0	0
Cash Flows from Financing Activities:
Debt issuance costs paid	0	0	0
Proceeds from debt	0	0	0
Repayments of debt	0	0	0
Discount due to loan modification			0
Intercompany note payable	0	0	0
Costs of issuance of common stock	(342)	(326)
Shares withheld to pay tax obligations related to employee stock compensation	(2,344)	(1,710)	(1,275)
Repurchases of common stock as part of announced plan	(7,943)	(158,860)	(54,802)
(Distributions to)/repayments from affiliates	97,016	281,073	178,812
Dividends paid and discount on dividend reinvestments	(91,601)	(126,516)	(125,183)
Net cash provided by/(used in) financing activities	(5,214)	(6,339)	(2,448)
Net increase/(decrease) in cash and cash equivalents	0	(1,640)	1,640
Cash and cash equivalents, beginning of year	150	1,790	150
Cash and cash equivalents, end of year	150	150	1,790
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net Cash Provided By/(Used In) Operating Activities	221,195	205,177	178,889
Cash Flows from Investing Activities:
Investment in real estate assets, consolidated joint venture, and real estate related intangibles, net of accruals	(454,836)	(489,241)	(267,918)
Intercompany note receivable	(71,900)	0	0
Redemption of noncontrolling interest in unconsolidated variable interest entity		(4,000)
Net sale proceeds from wholly-owned properties	165,698	696,612	16,713
Net sale proceeds received from unconsolidated joint ventures			0
Investments in unconsolidated joint ventures			0
Deferred lease costs paid	(23,138)	(33,891)	(23,222)
Net cash provided by/(used in) investing activities	(384,176)	169,480	(274,427)
Cash Flows from Financing Activities:
Debt issuance costs paid	0	(506)	0
Proceeds from debt	0	159,281	0
Repayments of debt	(168,875)	(106,301)	(575,702)
Discount due to loan modification			0
Intercompany note payable	81,060	(72,000)	(650)
Costs of issuance of common stock	0	0
Shares withheld to pay tax obligations related to employee stock compensation	0	0	0
Repurchases of common stock as part of announced plan	0	0	0
(Distributions to)/repayments from affiliates	250,862	(354,372)	670,716
Dividends paid and discount on dividend reinvestments	(15)	(15)	(15)
Net cash provided by/(used in) financing activities	163,032	(373,913)	94,349
Net increase/(decrease) in cash and cash equivalents	51	744	(1,189)
Cash and cash equivalents, beginning of year	3,117	2,373	3,562
Cash and cash equivalents, end of year	$ 3,168	$ 3,117	$ 2,373