Shareholders' Equity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 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			$ 2,038
Proceeds from exercise of stock options, shares			92
Tax benefit related to equity compensation			$ 651
Stock-based compensation expense			534
Amortization of restricted stock			5,044
Restricted stock granted, value			0
Restricted stock canceled			0
Dividends paid			(92,254)
Shares withheld for net settlements of share-based awards			(1,783)
Issuance of common stock (ESPP), value			218
Net income	$ 28,253	$ 38,898	57,010	$ 66,894
Other comprehensive loss	4,850	$ 641	(874)	$ 1,683
Ending Balance	1,016,577		1,016,577
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
Proceeds from exercise of stock options, value			$ 1
Proceeds from exercise of stock options, shares			92
Restricted stock granted, value			$ 4
Restricted stock granted, shares			423
Restricted stock canceled			$ 0
Restricted stock canceled (shares)			(15)
Shares withheld for net settlement of share-based awards (shares)			(41)
Issuance of common stock (ESPP), shares			6
Ending Balance	$ 747		$ 747
Ending Balance, shares	74,656		74,656
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			2,037
Tax benefit related to equity compensation			651
Stock-based compensation expense			534
Amortization of restricted stock			5,044
Restricted stock granted, value			(4)
Shares withheld for net settlements of share-based awards			(1,783)
Issuance of common stock (ESPP), value			218
Ending Balance	$ 872,753		872,753
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			(92,254)
Net income			57,068
Other comprehensive loss			0
Ending Balance	171,156		171,156
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			(851)
Ending Balance	(28,312)		(28,312)
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			314
Net income			(58)
Other comprehensive loss			(23)
Ending Balance	$ 233		$ 233