Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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	1,758,628	$ 1,962,636	3,474,129	$ 3,765,206
Pro forma	1,758,628	2,048,178	3,474,636	3,939,789
Net earnings from continuing operations [Abstract]
As reported	155,634	210,581	272,824	380,622
Pro forma	$ 155,634	$ 216,182	$ 278,947	$ 392,376
Basic earnings per share from continuing operations [Abstract]
As reported (in dollars per share)	$ 0.98	$ 1.26	$ 1.70	$ 2.26
Pro forma (in dollars per share)	0.98	1.30	1.74	2.33
Diluted earnings per share from continuing operations [Abstract]
As reported (in dollars per share)	0.97	1.25	1.69	2.23
Pro forma (in dollars per share)	$ 0.97	$ 1.28	$ 1.72	$ 2.30
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