Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ 1,045,993
Proceeds from exercise of stock options, value	1,215
Proceeds from exercise of stock options, shares	53,000
Tax benefit related to equity compensation	569
Stock-based compensation expense	432
Amortization of restricted stock	2,189
Restricted stock granted, value	0
Restricted stock canceled	0
Dividends paid	(45,977)
Shares withheld for net settlements of share-based awards	(1,123)
Issuance of common stock (ESPP), value	98
Net income	28,756	27,996
Other comprehensive loss	(5,721)	1,046
Ending Balance	1,026,431
Common shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	742
Beginning Balance, shares	74,191,000
Proceeds from exercise of stock options, value	0
Proceeds from exercise of stock options, shares	54,000
Restricted stock granted, value	4
Restricted stock granted, shares	396,000
Restricted stock canceled (shares)	(3,000)
Restricted stock canceled	0
Shares withheld for net settlement of share-based awards (shares)	(25,000)
Issuance of common stock (ESPP), shares	2,000
Ending Balance	746
Ending Balance, shares	74,615,000
Additional Paid-In Capital
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	866,056
Proceeds from exercise of stock options, value	1,215
Tax benefit related to equity compensation	569
Stock-based compensation expense	432
Amortization of restricted stock	2,189
Restricted stock granted, value	(4)
Shares withheld for net settlements of share-based awards	(1,123)
Issuance of common stock (ESPP), value	98
Ending Balance	869,432
Earnings in Excess of Distributions
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	206,342
Dividends paid	(45,977)
Net income	28,777
Other comprehensive loss	0
Ending Balance	189,142
Accumulated Other Comprehensive Loss
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	(27,461)
Other comprehensive loss	(5,705)
Ending Balance	(33,166)
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	314
Net income	(21)
Other comprehensive loss	(16)
Ending Balance	$ 277