Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Common stock [Member]	Additional paid-in capital ("APIC") [Member]	Retained earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Non-controlling interest ("NCI") [Member]	Contingently Redeemable Performance Share Units [Member]	Total
Balance at Dec. 31, 2018	$ 181,780	$ 56,885	$ 648,255	$ (56,277)	$ 5,067	$ 923	$ 835,710
Balance, shares at Dec. 31, 2018	108,682,030
Net income			97,466		109		97,575
Other comprehensive loss				(8,852)	(28)		(8,880)
Comprehensive income			97,466	(8,852)	81		88,695
Stock option exercises	$ 14,119	(1,679)					12,440
Stock option exercises, shares	544,576
Issuance of common stock related to vesting of share units	$ 5,886	(10,064)	1			(1,083)	(4,177)
Issuance of common stock related to vesting of share units, shares	207,403
Stock option compensation expense		4,852					4,852
Equity-classified PSU expense		8,640				114	8,640
Equity-classified PSU dividend equivalents		655	(700)			46	(45)
Cash dividends paid			(60,791)				(60,791)
Shares repurchased	$ (42,012)						(42,012)
Shares repurchased, shares	(1,223,674)
Balance at Sep. 30, 2019	$ 159,773	59,289	684,231	(65,129)	5,148		843,312
Balance, shares at Sep. 30, 2019	108,210,335
Balance at Jun. 30, 2019	$ 150,585	54,633	680,915	(55,449)	5,165	1,049	835,849
Balance, shares at Jun. 30, 2019	107,836,674
Net income			25,266		6		25,272
Other comprehensive loss				(9,680)	(23)		(9,703)
Comprehensive income			25,266	(9,680)	(17)		15,569
Stock option exercises	$ 8,451	(135)					8,316
Stock option exercises, shares	363,217
Issuance of common stock related to vesting of share units	$ 737		1			(1,083)	738
Issuance of common stock related to vesting of share units, shares	10,444
Stock option compensation expense		1,653					1,653
Equity-classified PSU expense		2,830				21	2,830
Equity-classified PSU dividend equivalents		308	(320)			$ 13	(12)
Cash dividends paid			(21,631)				(21,631)
Balance at Sep. 30, 2019	$ 159,773	59,289	684,231	(65,129)	5,148		843,312
Balance, shares at Sep. 30, 2019	108,210,335
Balance at Dec. 31, 2019	$ 194,771	52,110	714,051	(59,099)	5,154		906,987
Balance, shares at Dec. 31, 2019	109,337,781
Net income			121,239		199		121,438
Other comprehensive loss				7,415	30		7,445
Comprehensive income			121,239	7,415	229		128,883
Stock option exercises	$ 50,611	(10,417)					$ 40,194
Stock option exercises, shares	1,430,545						1,430,545
Issuance of common stock related to vesting of share units	$ 3,515	(7,459)					$ (3,944)
Issuance of common stock related to vesting of share units, shares	138,877
Stock option compensation expense		4,401					4,401
Equity-classified PSU expense		9,155					9,155
Equity-classified PSU dividend equivalents		463	(463)
Cash dividends paid			(67,639)				(67,639)
Shares repurchased	$ (53,170)						(53,170)
Shares repurchased, shares	(1,525,312)
Balance at Sep. 30, 2020	$ 195,727	48,253	767,188	(51,684)	5,383		964,867
Balance, shares at Sep. 30, 2020	109,381,891
Balance at Jun. 30, 2020	$ 169,255	47,958	746,048	(64,207)	5,254		904,308
Balance, shares at Jun. 30, 2020	108,630,537
Net income			45,387		103		45,490
Other comprehensive loss				12,523	26		12,549
Comprehensive income			45,387	12,523	129		58,039
Stock option exercises	$ 26,470	(5,701)					20,769
Stock option exercises, shares	751,268
Issuance of common stock related to vesting of share units	$ 2	(7)					(5)
Issuance of common stock related to vesting of share units, shares	86
Stock option compensation expense		1,671					1,671
Equity-classified PSU expense		4,138					4,138
Equity-classified PSU dividend equivalents		194	(194)
Cash dividends paid			(24,053)				(24,053)
Balance at Sep. 30, 2020	$ 195,727	$ 48,253	$ 767,188	$ (51,684)	$ 5,383		$ 964,867
Balance, shares at Sep. 30, 2020	109,381,891