CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock and Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Earnings (Loss)
Balance at beginning of period at Dec. 31, 2011	$ 1,579,029	$ 352,157	$ 1,238,866	$ (11,994)
Balance (in shares) at beginning of period at Dec. 31, 2011		154,969
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings for the year	222,398		222,398
Income tax benefit of common stock options exercised	39	39
Repurchase of common stock (in shares)		(10,466)
Repurchase of common stock	(214,195)	(214,195)
Common stock issued pursuant to stock-based compensation plans, net (in shares)		1,311
Common stock issued pursuant to stock-based compensation plans, net	7,644	7,644
Stock-based compensation expense	25,901	25,901
Dividends paid	(42,450)		(42,450)
Other comprehensive income (loss)	21,535			21,535
Balance at end of period at Dec. 31, 2012	1,599,901	171,546	1,418,814	9,541
Balance (in shares) at end of period at Dec. 31, 2012		145,814
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings for the year	177,015		177,015
Income tax benefit of common stock options exercised	551	551
Repurchase of common stock (in shares)		(5,988)
Repurchase of common stock	(162,078)	(162,078)
Common stock issued pursuant to stock-based compensation plans, net (in shares)		956
Common stock issued pursuant to stock-based compensation plans, net	4,849	4,849
Stock-based compensation expense	28,087	28,087
Dividends paid	(51,404)		(51,404)
Other comprehensive income (loss)	16,459			16,459
Balance at end of period at Dec. 31, 2013	1,613,380	42,955	1,544,425	26,000
Balance (in shares) at end of period at Dec. 31, 2013		140,782
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings for the year	200,261		200,261
Income tax benefit of common stock options exercised	12,751	12,751
Repurchase of common stock (in shares)		(4,243)
Repurchase of common stock	(139,238)	(122,851)	(16,387)
Common stock issued pursuant to stock-based compensation plans, net (in shares)		3,040
Common stock issued pursuant to stock-based compensation plans, net	37,774	37,774
Stock-based compensation expense	30,767	30,767
Dividends paid	(56,513)		(56,513)
Other comprehensive income (loss)	(89,409)			(89,409)
Balance at end of period at Dec. 31, 2014	$ 1,609,773	$ 1,396	$ 1,671,786	$ (63,409)
Balance (in shares) at end of period at Dec. 31, 2014		139,579