Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-In Capital	(Distributions in Excess of Earnings/Earnings in Excess of Distributions	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Noncontrolling Interest
Beginning Balance at Dec. 31, 2015		$ 1,006,837	$ 1,121	$ 879,225	$ 158,796	$ (32,404)	$ 0	$ 99
Beginning Balance (in shares) at Dec. 31, 2015			111,966				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised		3,347	$ 2	3,345
Proceeds from stock options exercised (in shares)			234
Tax benefit related to equity compensation		(1,626)		(1,626)
Stock based compensation expense		12,773		12,773
Shares withheld for net settlements of share-based awards (in shares)			(113)				0
Shares withheld for net settlements of share-based awards		(2,337)	$ (2)	(2,335)			$ 0
Restricted stock granted		0	$ 5	(5)
Restricted stock granted (in shares)			523
Restricted stock canceled		0	$ (1)	1
Restricted stock canceled (in shares)			(84)
Dividends - paid		(194,748)			(194,748)
Re-issuance of treasury shares (ESPP) (in shares)			22				0
Re-issuance of treasury shares (ESPP)		436		436	0		$ 0
Net income (loss)		148,498			148,715			(217)
Other comprehensive income (loss)		1,598				1,579		19
Ending Balance at Dec. 31, 2016		974,957	$ 1,125	891,993	112,763	(30,825)	$ 0	(99)
Ending Balance (in shares) at Dec. 31, 2016			112,548				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised		6,962	$ 4	6,958
Proceeds from stock options exercised (in shares)			358
Stock based compensation expense		19,844		19,844
Shares withheld for net settlements of share-based awards (in shares)			(136)				0
Shares withheld for net settlements of share-based awards		(4,142)		(4,141)			$ 0
Restricted stock granted		0	$ 9	(9)
Restricted stock granted (in shares)			933
Restricted stock canceled		0	$ (1)	1
Restricted stock canceled (in shares)			(65)
Dividends - paid		(227,463)			(227,463)
Issuance of common stock - prospectus supplement (in shares)			10,350
Issuance of common stock - prospectus supplement		275,867	$ 104	275,763	0
Issuance of common stock (ESPP) (in shares)			20
Issuance of common stock (ESPP)		497		497
Net income (loss)		146,024			146,241			(217)
Other comprehensive income (loss)		6,373				6,379		(6)
Ending Balance at Dec. 31, 2017		1,198,919	$ 1,240	1,190,906	31,541	(24,446)	$ 0	(322)
Ending Balance (in shares) at Dec. 31, 2017			124,008				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from stock options exercised		$ 1,887	$ 1	1,886
Proceeds from stock options exercised (in shares)		103	103
Stock based compensation expense		$ 22,049		22,049
Shares withheld for net settlements of share-based awards (in shares)			(173)
Shares withheld for net settlements of share-based awards		(3,820)	$ (2)	(3,818)
Restricted stock granted		0	$ 9	(9)
Restricted stock granted (in shares)			906
Restricted stock canceled		0	$ 0	0
Restricted stock canceled (in shares)			(73)
Dividends - paid		(229,498)			(229,498)
Purchase of treasury shares (in shares)							4,210
Purchase of treasury shares		(95,175)					$ (95,175)
Issuance of common stock (ESPP) (in shares)			24
Issuance of common stock (ESPP)		534		534
Other Adjustments to Additional Paid-in Capital	[1]	(632)		(632)
Net income (loss)		144,827			145,089			(262)
Other comprehensive income (loss)		813				828		(15)
Ending Balance at Dec. 31, 2018		$ 1,039,904	$ 1,248	$ 1,210,916	$ (52,868)	$ (23,618)	$ (95,175)	$ (599)
Ending Balance (in shares) at Dec. 31, 2018			120,585				4,210

[1] Represents a cumulative-effect adjustment upon adoption of ASU No. 2016-16, "Income Taxes - Intra-Entity Transfers of Assets Other Than Inventory." Refer to Note 1 - Summary of Business Organization, Operations and Significant Accounting Policies - Recent Accounting Pronouncements for further information.