Share-Based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Additional Disclosures [Abstract]
Total pre-tax share-based compensation recognized in the Consolidated Statements of Earnings	$ 500	$ 5,900	$ 7,700
Tax related (costs) benefits	(300)	500	2,800
Cash received from the exercise of stock options	$ 100	$ 300	$ 700
Non-vested Stock [Member]
Stock Unit Activity [Roll Forward]
Outstanding, beginning of period (in shares)	412	435	542
Granted (in shares)	142	115	119
Vested (in shares)	(111)	(114)	(172)
Cancelled (in shares)	(63)	(24)	(54)
Outstanding, end of period (in shares)	380	412	435
Grant Date Weighted Average Fair Value [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 65.64	$ 56.44	$ 48.94
Granted (in dollars per share)	59.45	74.26	69.92
Vested (in dollars per share)	56.91	39.75	43.42
Cancelled (in dollars per share)	64.71	63.62	52.41
Outstanding, end of period (in dollars per share)	$ 66.02	$ 65.64	$ 56.44
Outstanding, aggregate intrinsic value	$ 21,239	$ 30,113	$ 34,184	$ 34,063
Additional Disclosures [Abstract]
Total intrinsic values of shares vested	7,700	$ 8,800	$ 12,800
Non-vested Stock and Performance Stock Units [Member]
Additional Disclosures [Abstract]
Compensation cost net yet recognized	$ 12,500
Compensation cost not yet recognized, period for recognition	1 year 5 months 23 days
2017 Stock Plan [Member] | Non-vested Stock [Member]
Share-based Compensation Arrangement [Abstract]
Number of shares authorized for issuance (in shares)	1,800
Number of shares available for grant (in shares)	1,600
Award vesting period	3 years
Percentage of grants to elected officers that will be performance stock unit awards	100.00%	100.00%	100.00%
Percentage of stated performance metrics award of grant	150.00%	150.00%	150.00%
Number of years to measure performance metrics	3 years	3 years	3 years