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
Changes in Total Equity
Impact of change in accounting policy (Note 2) | Adjustments for New Accounting Pronouncement | ASU 2014-09					$ (4,445)		$ (4,445)
Adjusted balance as of January 1, 2018	$ 20,277	$ 162,806	$ (36,148)	$ (909,960)	2,999,573		2,236,548
Balance (Previously reported) at Dec. 31, 2017						$ 115,689
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 repurchase of noncontrolling interests						(1)
Balance at Mar. 31, 2018						$ 126,000
Balance (Previously reported) at Dec. 31, 2017	$ 20,277	162,806	(36,148)	(909,960)	3,004,018		$ 2,240,993
Balance (in shares) (Previously reported) at Dec. 31, 2017	202,765
Balance (in shares) at Dec. 31, 2017	202,765						202,765,000
Changes in Total Equity
Net income					141,841		$ 141,841
Other comprehensive income			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		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						202,765,000