Acquisitions - Progressive Acquisition Pro Forma Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Revenues, as reported	$ 767,694	$ 698,418	$ 2,358,557	$ 1,946,331
Net earnings, as reported	$ 24,194	$ 9,295	$ 113,983	56,139
Progressive
Business Acquisition [Line Items]
Revenues, as reported				1,946,331
Net earnings, as reported				56,139
Revenues, pro forma				2,102,929
Net earnings, pro forma				$ 61,601