Business Segment Information - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total gross profit from reportable segments	$ 108,049	$ 144,491	$ 80,369	$ 56,283	$ 100,707	$ 114,530	$ 74,570	$ 25,126	$ 389,192	$ 314,933	$ 301,370
Selling, general and administrative expenses									272,776	220,400	217,374
Acquisition and integration expenses									60,045	0	0
Gain on sales of property and equipment									(7,672)	(4,182)	(8,358)
Total other income									(112)	(5,748)	(4,008)
Income before provision for income taxes									64,155	104,463	96,362
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total gross profit from reportable segments									$ 389,192	$ 314,933	$ 301,370