CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2017	$ 676,334	$ 353,392	$ 321,408	$ 1,534
Beginning balance (in shares) at Dec. 31, 2017		50,248
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,269
Other comprehensive income/loss	4,072			4,072
Stock-based compensation expense	1,256	$ 1,256
Options exercised	1,286	$ 1,286
Options exercised (in shares)		91
Issuance of common stock under Employee Stock Purchase Plans	294	$ 294
Issuance of common stock under Employee Stock Purchase Plans (in shares)		7
Ending balance at Mar. 31, 2018	688,511	$ 356,228	326,677	5,606
Ending balance (in shares) at Mar. 31, 2018		50,346
Beginning balance at Dec. 31, 2018	$ 932,775	$ 571,383	363,425	(2,033)
Beginning balance (in shares) at Dec. 31, 2018	54,893	54,893
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 6,195
Other comprehensive income/loss	(2,515)			(2,515)
Stock-based compensation expense	1,766	$ 1,766
Options exercised	1,365	$ 1,365
Options exercised (in shares)		95
Issuance of common stock under Employee Stock Purchase Plans	432	$ 432
Issuance of common stock under Employee Stock Purchase Plans (in shares)		7
Ending balance at Mar. 31, 2019	$ 940,111	$ 574,946	$ 369,713	$ (4,548)
Ending balance (in shares) at Mar. 31, 2019	54,995	54,995