CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands	Total	Total Shareholders’ Equity	Common Shares	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Retained Earnings	Noncontrolling Interests
Balance (in Shares) at Dec. 31, 2015	70,258,415		70,258,000
Balance at period start at Dec. 31, 2015	$ 1,521,354	$ 1,100,488	$ 70	$ 1,092,239	$ (4,463)	$ 12,642	$ 420,866
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership (in Shares)			350,000
Conversion of OP Units to Common Shares by limited partners of the Operating Partnership	0	7,875	$ 1	7,874			(7,875)
Issuance of Common Shares, net of issuance costs (in Shares)			10,228,000
Issuance of Common Shares, net of issuance costs	357,262	357,262	$ 10	357,252
Issuance of OP Units to Acquire Real Estate	29,336						29,336
Dividends and dividend equivalents declared ($0.75 per Common Share)	(61,180)	(56,782)				(56,782)	(4,398)
Employee and trustee stock compensation, net (in Shares)			27,000
Employee and trustee stock compensation, net	11,682	699		699			10,983
Acquisition of noncontrolling interests	(18,379)	7,546		7,546			(25,925)
Change in control of previously consolidated investment	(75,713)						(75,713)
Noncontrolling interest distributions	(50,849)						(50,849)
Noncontrolling interest contributions	204,412						204,412
Reallocation of noncontrolling interest	0	35,254		35,254			(35,254)
Balance before adjustment towards comprehensive income (in Shares)			80,863,000
Balance before adjustment towards comprehensive income	1,917,925	1,452,342	$ 81	1,500,864	(4,463)	(44,140)	465,583
Comprehensive (loss) income:
Net income	100,356	52,955				52,955	47,401
Unrealized loss on valuation of swap agreements	(12,624)	(11,351)			(11,351)		(1,273)
Reclassification of realized interest on swap agreements	3,396	2,970			2,970		426
Comprehensive income	$ 91,128	44,574			(8,381)	52,955	46,554
Balance (in Shares) at Sep. 30, 2016	80,863,404		80,863,000
Balance at period end at Sep. 30, 2016	$ 2,009,053	$ 1,496,916	$ 81	$ 1,500,864	$ (12,844)	$ 8,815	$ 512,137