Shareholders' Equity - Changes in Shareholders' Equity (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ 1,026,904	$ 1,039,904	$ 1,138,572	$ 1,198,919	$ 1,039,904	$ 1,198,919
Proceeds from exercise of stock options	739	333	1,111	261
Proceeds from exercise of stock options (shares)					64
Stock-based compensation expense	5,453	6,727	4,960	5,827
Restricted stock granted	0	0	0
Restricted stock canceled	0	0	0	0
Dividends paid	(58,177)	(57,945)	(56,698)	(58,319)
Shares withheld for net settlements of share-based awards		(4,172)	(34)	(4,357)
Issuance of common stock - ESPP	128	124	123	141
Repurchases of common stock			(30,264)	(40,182)
Transition adjustment for accounting standard adoption							$ 0
Net income (loss)	41,836	40,649	37,325	34,920	$ 82,485	72,245
Other comprehensive income	4,654		(2,158)	1,362	6,902	(796)
Ending Balance	1,021,538	1,026,904	1,092,937	1,138,572	1,021,538	1,092,937
Common shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ 1,254	$ 1,248	$ 1,239	$ 1,240	$ 1,248	$ 1,240
Beginning Balance (shares)	121,187	120,585	122,005	124,008	120,585	124,008
Proceeds from exercise of stock options	$ 0	$ 0	$ 0	$ 1
Proceeds from exercise of stock options (shares)	42	22	62	15
Restricted stock granted	$ 0	$ 8	$ 9
Restricted stock granted (shares)	10	778	896
Restricted stock canceled	$ 0	$ 0	$ 0	$ 0
Restricted stock canceled (shares)	(32)	(6)	(19)	(9)
Shares withheld for net settlements of share-based awards		$ (2)	$ 0	$ (2)
Shares withheld for net settlements of share-based awards (shares)		(198)	(2)	(169)
Issuance of common stock - ESPP (shares)	6	6	4	8
Repurchases of common stock (shares)			(1,269)	(1,848)
Ending Balance	$ 1,254	$ 1,254	$ 1,248	$ 1,239	$ 1,254	$ 1,248
Ending Balance (shares)	121,213	121,187	121,677	122,005	121,213	121,677
Additional Paid-In Capital
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ 1,213,922	$ 1,210,916	$ 1,192,779	$ 1,190,906	$ 1,210,916	$ 1,190,906
Proceeds from exercise of stock options	739	333	1,111	260
Stock-based compensation expense	5,453	6,727	4,960	5,827
Restricted stock granted	0	(8)	(9)
Shares withheld for net settlements of share-based awards		(4,170)	(34)	(4,355)
Issuance of common stock - ESPP	128	124	123	141
Ending Balance	1,220,242	1,213,922	1,198,930	1,192,779	1,220,242	1,198,930
Earnings in Excess of Distributions
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	(71,076)	(52,868)	8,209	31,541	(52,868)	31,541
Dividends paid	(58,177)	(57,945)	(56,698)	(58,319)
Transition adjustment for accounting standard adoption							(968)
Net income (loss)	41,914	40,705	37,421	34,987
Ending Balance	(87,339)	(71,076)	(11,068)	8,209	(87,339)	(11,068)
Accumulated Other Comprehensive Loss
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	(21,366)	(23,618)	(23,092)	(24,446)	(23,618)	(24,446)
Transition adjustment for accounting standard adoption							$ 968
Other comprehensive income			(2,137)	1,354	6,902	(783)
Ending Balance	(16,716)	(21,366)	(25,229)	(23,092)	(16,716)	(25,229)
Treasury shares
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ (95,175)	$ (95,175)	$ (40,182)	$ 0	$ (95,175)	$ 0
Beginning Balance (shares)	4,210	4,210	1,848	0	4,210	0
Repurchases of common stock			$ (30,264)	$ (40,182)
Repurchases of common stock (shares)			1,269	1,848
Ending Balance	$ (95,175)	$ (95,175)	$ (70,446)	$ (40,182)	$ (95,175)	$ (70,446)
Ending Balance (shares)	4,210	4,210	3,117	1,848	4,210	3,117
Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Beginning Balance	$ (655)	$ (599)	$ (381)	$ (322)	$ (599)	$ (322)
Net income (loss)	(78)	(56)	(96)	(67)
Other comprehensive income			(21)	8
Ending Balance	(728)	(655)	$ (498)	$ (381)	$ (728)	$ (498)
Accounting Standards Update 2016-02
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Other comprehensive income	4,655	1,284
Accounting Standards Update 2016-02 | Accumulated Other Comprehensive Loss
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Other comprehensive income	4,650	1,284
Accounting Standards Update 2016-02 | Noncontrolling Interests
Changes in shareholders' equity that are attributable to the Company's shareholders and to non controlling interests
Other comprehensive income	$ 5	$ 0