Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Retained Earnings	Redeemable Noncontrolling Interest	Total
Balance at Dec. 31, 2017						$ 115,689
Changes in Redeemable Noncontrolling Interests
Net income						1,261
Adjustments to redemption value of redeemable noncontrolling interest						9,051
Subsidiary dividends paid to noncontrolling interests						(1)
Balance at Mar. 31, 2018						126,000
Balance at Dec. 31, 2017	$ 20,277	$ 162,806	$ (36,148)	$ (909,960)	$ 3,004,018		$ 2,240,993
Balance (in shares) at Dec. 31, 2017	202,765
Changes in Total Equity
Net income					141,841		141,841
Other comprehensive income (loss)			14,929				14,929
Common stock issued from treasury shares for exercise of stock options		5,199		21,258			26,457
Common stock unissued due to forfeiture of nonvested awards		551		(551)
Common stock issued from treasury shares for nonvested awards		(12,368)		12,368
Common stock issued from treasury for dividend equivalents		925		9			934
Share-based compensation (Note 7)		6,835					6,835
Cash dividends declared ($0.13 per share)					(23,895)		(23,895)
Purchase of treasury shares				(24)			(24)
Adjustments to redemption value of redeemable noncontrolling interest		(9,051)					(9,051)
Balance at Mar. 31, 2018	$ 20,277	154,897	(21,219)	(876,900)	3,117,519		2,394,574
Balance (in shares) at Mar. 31, 2018	202,765
Balance at Dec. 31, 2017						115,689
Balance at Dec. 31, 2017	$ 20,277	162,806	(36,148)	(909,960)	3,004,018		2,240,993
Balance (in shares) at Dec. 31, 2017	202,765
Changes in Total Equity
Other comprehensive income (loss)							(8,874)
Balance at Jun. 30, 2018	$ 20,277	165,137	(45,022)	(874,742)	3,236,046		2,501,696
Balance (in shares) at Jun. 30, 2018	202,765
Changes in Total Equity
Cumulative effect adjustment from adoption of ASU No. 2014-09 (Note 3) | ASU 2014-09					(4,445)		(4,445)
Balance at Mar. 31, 2018						126,000
Changes in Redeemable Noncontrolling Interests
Subsidiary repurchase of noncontrolling interests						(126,000)
Subsidiary dividends paid to noncontrolling interests						(3,777)
Balance at Mar. 31, 2018	$ 20,277	154,897	(21,219)	(876,900)	3,117,519		2,394,574
Balance (in shares) at Mar. 31, 2018	202,765
Changes in Total Equity
Net income					142,435		142,435
Other comprehensive income (loss)			(23,803)				(23,803)
Common stock issued from treasury shares for exercise of stock options		1,110		1,717			2,827
Common stock unissued due to forfeiture of nonvested awards		78		(78)
Common stock issued from treasury shares for nonvested awards		(577)		577
Share-based compensation (Note 7)		13,406					13,406
Cash dividends declared ($0.13 per share)					(23,908)		(23,908)
Purchase of treasury shares				(58)			(58)
Adjustments to redemption value of redeemable noncontrolling interest		(3,777)				$ 3,777	(3,777)
Balance at Jun. 30, 2018	$ 20,277	165,137	(45,022)	(874,742)	3,236,046		2,501,696
Balance (in shares) at Jun. 30, 2018	202,765
Balance at Dec. 31, 2018	$ 20,277	189,889	(60,223)	(1,042,687)	3,478,650		$ 2,585,906
Balance (in shares) at Dec. 31, 2018	202,765						202,765,000
Changes in Total Equity
Net income					161,607		$ 161,607
Other comprehensive income (loss)			10,247				10,247
Common stock issued from treasury shares for exercise of stock options		3,485		2,981			6,466
Common stock unissued due to forfeiture of nonvested awards		77		(77)
Common stock issued from treasury shares for nonvested awards		(12,812)		12,812
Share-based compensation (Note 7)		11,296					11,296
Cash dividends declared ($0.13 per share)					(22,546)		(22,546)
Purchase of treasury shares				(400,013)			(400,013)
Balance at Mar. 31, 2019	$ 20,277	191,935	(55,028)	(1,426,984)	3,622,560		2,352,760
Balance (in shares) at Mar. 31, 2019	202,765
Balance at Dec. 31, 2018	$ 20,277	189,889	(60,223)	(1,042,687)	3,478,650		$ 2,585,906
Balance (in shares) at Dec. 31, 2018	202,765						202,765,000
Changes in Total Equity
Other comprehensive income (loss)							$ 1,075
Balance at Jun. 30, 2019	$ 20,277	203,098	(64,200)	(1,426,177)	3,761,596		$ 2,494,594
Balance (in shares) at Jun. 30, 2019	202,765						202,765,000
Changes in Total Equity
Cumulative effect adjustment from adoption of ASU No. 2014-09 (Note 3) | Adjustments for New Accounting Pronouncement | ASU 2016-01			(5,052)		5,052
Cumulative effect adjustment from adoption of ASU No. 2014-09 (Note 3) | Adjustments for New Accounting Pronouncement | ASU 2016-02					(203)		$ (203)
Balance at Mar. 31, 2019	$ 20,277	191,935	(55,028)	(1,426,984)	3,622,560		2,352,760
Balance (in shares) at Mar. 31, 2019	202,765
Changes in Total Equity
Net income					162,760		162,760
Other comprehensive income (loss)			(9,172)				(9,172)
Common stock issued from treasury shares for exercise of stock options		30		416			446
Common stock issued from treasury shares for nonvested awards		(401)		401
Common stock issued from treasury for dividend equivalents		602					602
Share-based compensation (Note 7)		10,932					10,932
Cash dividends declared ($0.13 per share)					(23,724)		(23,724)
Purchase of treasury shares				(10)			(10)
Balance at Jun. 30, 2019	$ 20,277	$ 203,098	$ (64,200)	$ (1,426,177)	$ 3,761,596		$ 2,494,594
Balance (in shares) at Jun. 30, 2019	202,765						202,765,000