Shareholders' Equity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 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			$ 2,513
Proceeds from exercise of stock options, shares			109
Tax benefit related to equity compensation			$ 1,252
Stock-based compensation expense			8,602
Restricted stock granted, value			0
Restricted stock canceled			0
Dividends paid			(138,454)
Shares withheld for net settlements of share-based awards			(2,748)
Issuance of common stock (ESPP), value			321
Net income	$ 38,291	$ 38,965	95,295	$ 105,859
Other comprehensive loss	(6,441)	$ (7,983)	(7,315)	$ (6,301)
Ending Balance	1,005,459		1,005,459
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			$ 0
Proceeds from exercise of stock options, shares			109
Restricted stock granted, value			$ 4
Restricted stock granted, shares			423
Restricted stock canceled			$ 0
Restricted stock canceled (shares)			(27)
Shares withheld for net settlement of share-based awards (shares)			(71)
Issuance of common stock (ESPP), shares			9
Ending Balance	$ 746		$ 746
Ending Balance, shares	74,634		74,634
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			2,513
Tax benefit related to equity compensation			1,252
Stock-based compensation expense			8,602
Restricted stock granted, value			(4)
Shares withheld for net settlements of share-based awards			(2,748)
Issuance of common stock (ESPP), value			321
Ending Balance	$ 875,992		875,992
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			(138,454)
Net income			95,374
Other comprehensive loss			0
Ending Balance	163,262		163,262
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			(7,249)
Ending Balance	(34,710)		(34,710)
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			314
Net income			(79)
Other comprehensive loss			(66)
Ending Balance	$ 169		$ 169