Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill - tax deductible	$ 2,076		$ 2,076
Net cash consideration			6,500		$ 366,532
Revenue from continuing operations [Abstract]
As reported	1,787,582	$ 2,009,575	5,261,711	$ 5,774,781
Pro forma	1,787,582	2,079,626	5,262,218	6,019,415
Net earnings from continuing operations [Abstract]
As reported	186,483	225,683	459,307	606,305
Pro forma	$ 186,483	$ 231,805	$ 465,430	$ 624,180
Basic earnings per share from continuing operations [Abstract]
As reported (in dollars per share)	$ 1.20	$ 1.36	$ 2.90	$ 3.62
Pro forma (in dollars per share)	1.20	1.40	2.94	3.73
Diluted earnings per share from continuing operations [Abstract]
As reported (in dollars per share)	1.19	1.34	2.87	3.57
Pro forma (in dollars per share)	$ 1.19	$ 1.38	$ 2.91	$ 3.68
Customer Relationships [Member]
Business Acquisition [Line Items]
Acquired finite-lived intangible asset, amount			$ 2,500
Acquired finite-lived intangible assets, weighted average useful life			7 years
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Acquired finite-lived intangible asset, amount			$ 300
Acquired finite-lived intangible assets, weighted average useful life			3 years
Accelerated Companies [Member]
Business Acquisition [Line Items]
Net cash consideration					$ 435,722