Acquisitions (Details) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Dec. 31, 2016 USD ($) Acquisitions
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired			$ 25,568	$ 475,236
Goodwill, Acquired During Period			$ 24,649	301,577
Finite-lived Intangible Assets Acquired				192,065
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net					$ 1,562,000
Business Combination, Assets and Liabilities Arising from Contingencies, Amount Recognized, Net					$ 1,554,000
Document Fiscal Year Focus			2017
Number of Businesses Acquired | Acquisitions					6
Revenue [Abstract]
As reported	$ 1,993,351	$ 1,686,345	$ 3,806,723	3,308,618
Pro forma	1,993,483	1,877,659	3,809,834	3,698,831
Net earnings [Abstract]
As reported	164,058	118,290	336,305	217,646
Pro forma	$ 164,209	$ 124,926	$ 336,756	$ 235,219
Basic earnings per share [Abstract]
As reported (in dollars per share) | $ / shares	$ 1.05	$ 0.76	$ 2.16	$ 1.40
Pro forma (in dollars per share) | $ / shares	1.05	0.81	2.16	1.52
Diluted earnings per share [Abstract]
As reported (in dollars per share) | $ / shares	1.04	0.76	2.14	1.39
Pro forma (in dollars per share) | $ / shares	$ 1.04	$ 0.80	$ 2.14	$ 1.50
Caldera Graphics [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition of 100 Percent, Voting Rights			100.00%
Payments to Acquire Businesses, Net of Cash Acquired			$ 32,680
Goodwill, Acquired During Period			24,649
Finite-lived Intangible Assets Acquired			$ 8,169
Minimum [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				10 years
Minimum [Member] | Caldera Graphics [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			7 years
Maximum [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				15 years
Maximum [Member] | Caldera Graphics [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			15 years