Consolidated Statement of Shareholders' Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]
Balance (in shares) at Dec. 31, 2016	43,569,000	43,569,000
Balance at Dec. 31, 2016	$ 160,320	$ 436	$ 0	$ 159,884
Net income	49,286			49,286
Exercise of common stock options (in shares)		212,000
Exercise of common stock options	3,040	$ 2	3,038	0
Stock-based compensation (in shares)		587,000
Stock-based compensation	11,809	$ 6	11,803	0
Repurchases of common stock (in shares)		(4,549,000)
Repurchases of common stock	$ (120,158)	$ (46)	(14,841)	(105,271)
Balance (in shares) at Sep. 30, 2017	39,819,000	39,819,000
Balance at Sep. 30, 2017	$ 104,297	$ 398	$ 0	$ 103,899