Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Income per share
Strike price of the warrant transactions (in dollars per share)	$ 80.9063						$ 80.9063
Numerator, dollars in thousands:
Net earnings	$ 39,997	$ 34,667	$ 21,518	$ 28,860	$ 32,727	$ 18,340	$ 96,182	$ 79,927
Denominator:
Weighted average shares outstanding, basic (in shares)	52,658,850			52,453,384			52,583,891	52,392,232
Effect of dilutive securities:
Stock options, RSU and SAR (in shares)	1,103,792			1,352,454			1,079,382	1,506,254
Weighted average shares outstanding, diluted (in shares)	53,762,642			53,805,838			53,663,273	53,898,486
Earnings per share, basic (in dollars per share)	$ 0.76			$ 0.55			$ 1.83	$ 1.53
Earnings per share, diluted (in dollars per share)	$ 0.74			$ 0.54			$ 1.79	$ 1.48
Stock options, RSUs, PSUs
Income per share
Common stock equivalents excluded in the calculation of diluted income per share (in shares)	2,677,770			1,395,138			2,905,469	961,605
2023 Notes
Income per share
Conversion price, per share of common stock (in dollars per share)	$ 59.33						$ 59.33