Supplementary Financial Data Supplementary Financial Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplementary Financial Data [Abstract]
Revenue	$ 742,150	$ 653,345	$ 623,686	$ 481,109	$ 722,485	$ 567,842	$ 558,098	$ 437,857	$ 2,500,290	$ 2,286,282	$ 1,961,971
Gross margin	142,775	134,181	119,829	92,642	130,039	115,813	108,762	89,155
Net Income Available to Common Stockholders	$ 41,780	$ 37,838	$ 30,246	$ 17,723	$ 32,407	$ 29,282	$ 27,911	$ 18,063	$ 127,587	$ 107,663	$ 66,168
Earnings Per Share, Basic	$ 1.48	$ 1.35	$ 1.10	$ 0.64	$ 1.17	$ 1.03	$ 0.98	$ 0.64	$ 4.58	$ 3.81	$ 2.57
Earnings Per Share, Diluted	$ 1.44	$ 1.32	$ 1.08	$ 0.63	$ 1.15	$ 1.01	$ 0.96	$ 0.60	$ 4.48	$ 3.70	$ 2.26
Basic Weighted Average Shares Outstanding	28,297	27,981	27,599	27,498	27,774	28,469	28,571	28,124	27,846	28,234	25,769
Diluted Weighted Average Shares Outstanding	29,049	28,598	28,090	27,970	28,181	28,906	29,101	30,544	28,475	29,178	30,688
Purchase Accounting Adjustments		$ 100	$ 100	$ 400	$ 600	$ 700	$ 3,000	$ 900
Total valuation adjustments and write-offs	$ 5,000				$ 5,800				$ 5,000	$ 5,800	$ 7,700