Shareholders' Equity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			$ 1,198,919
Proceeds from exercise of stock options			$ 1,781
Proceeds from exercise of stock options (shares)			97
Stock-based compensation expense			$ 16,351
Restricted stock granted			0
Restricted stock canceled			0
Dividends paid			(172,256)
Shares withheld for net settlements of share-based awards			(4,452)
Issuance of common stock - ESPP			404
Repurchases of common stock			(70,446)
Net income (loss)	$ 39,229	$ 38,453	111,474	$ 109,761
Other comprehensive loss	(556)	$ 1,625	(1,363)	$ 4,761
Ending Balance	1,080,412		1,080,412
Common shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			$ 1,240
Beginning Balance, shares			124,008
Proceeds from exercise of stock options			$ 1
Proceeds from exercise of stock options (shares)			97
Restricted stock granted			$ 9
Restricted stock granted (shares)			905
Restricted stock canceled			$ 0
Restricted stock canceled (shares)			(52)
Shares withheld for net settlements of share-based awards			$ (2)
Shares withheld for net settlements of share-based awards (shares)			(173)
Issuance of common stock - ESPP (shares)			18
Repurchases of common stock (shares)			(3,117)
Ending Balance	$ 1,248		$ 1,248
Ending Balance, shares	121,686		121,686
Additional Paid-In Capital
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			$ 1,190,906
Proceeds from exercise of stock options			1,780
Stock-based compensation expense			16,351
Restricted stock granted			(9)
Shares withheld for net settlements of share-based awards			(4,450)
Issuance of common stock - ESPP			404
Ending Balance	$ 1,204,982		1,204,982
Earnings in Excess of Distributions
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			31,541
Dividends paid			(172,256)
Net income (loss)			111,697
Ending Balance	(29,018)		(29,018)
Accumulated Other Comprehensive Loss
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			(24,446)
Other comprehensive loss			(1,339)
Ending Balance	(25,785)		(25,785)
Treasury shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			$ 0
Beginning Balance, shares			0
Repurchases of common stock			$ (70,446)
Repurchases of common stock (shares)			3,117
Ending Balance	$ (70,446)		$ (70,446)
Ending Balance, shares	3,117		3,117
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance			$ (322)
Net income (loss)			(223)
Other comprehensive loss			(24)
Ending Balance	$ (569)		$ (569)