Shareholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Mar. 07, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		$ 974,957
Proceeds from exercise of stock options, shares		195,000
Proceeds from exercise of stock options, value		$ 3,882
Stock-based compensation expense		4,963
Restricted stock granted, value		0
Restricted stock canceled		0
Dividends paid		(52,504)
Issuance of common stock - prospectus supplement		$ 276,036
Issuance of common stock - prospectus supplement (shares)	9,000,000	10,350,000
Shares withheld for net settlements of share-based awards		$ (3,434)
Re-issuance of treasury shares - ESPP		122
Net income		40,366	$ 32,326
Other comprehensive income		1,260	$ (898)
Ending Balance		1,245,648		$ 974,957
Common shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		$ 1,125
Beginning Balance, shares		112,548,000
Proceeds from exercise of stock options, shares		195,000
Proceeds from exercise of stock options, value		$ 2
Restricted stock granted, value		$ 6
Restricted stock granted, shares		622,000
Restricted stock canceled (shares)		(11,000)
Issuance of common stock - prospectus supplement		$ 104
Issuance of common stock - prospectus supplement (shares)		10,350,000
Shares withheld for net settlements of share-based awards				(1)
Shares withheld for net settlements of share-based awards (shares)		(113,000)
Re-issuance of treasury shares - ESPP (shares)		4,000
Ending Balance		$ 1,236		$ 1,125
Ending Balance, shares		123,595,000		112,548,000
Additional Paid-In Capital
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		$ 891,993
Proceeds from exercise of stock options, value		3,880
Stock-based compensation expense		4,963
Restricted stock granted, value		(6)
Issuance of common stock - prospectus supplement		275,932
Shares withheld for net settlements of share-based awards		(3,433)
Re-issuance of treasury shares - ESPP		122
Ending Balance		1,173,451		$ 891,993
Earnings in Excess of Distributions
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		112,763
Dividends paid		(52,504)
Net income		40,403
Ending Balance		100,662		112,763
Accumulated Other Comprehensive Loss
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		(30,825)
Other comprehensive income		1,258
Ending Balance		(29,567)		(30,825)
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance		(99)
Net income		(37)
Other comprehensive income		2
Ending Balance		$ (134)		$ (99)