Subsequent Events (Details) $ / shares in Units, $ in Thousands, £ in Millions		1 Months Ended		3 Months Ended
	Apr. 26, 2018 $ / shares	Apr. 30, 2018 GBP (£) shares	Apr. 30, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares	Apr. 01, 2017 USD ($) $ / shares	May 08, 2018 USD ($)
Subsequent Events
Common stock quarterly cash dividend declared (in dollars per share) | $ / shares				$ 0.17	$ 0.14
Borrowings under revolving line of credit				$ 10,000	$ 6,000
Amount available for future repurchases				$ 21,200
Subsequent Events
Subsequent Events
Common stock quarterly cash dividend declared (in dollars per share) | $ / shares	$ 0.17
Shares repurchased under share repurchase program | shares		215,585	215,585
Shares retired under share repurchase program | shares		215,585	215,585
Share repurchases, Average price per share (in dollars per share) | $ / shares			$ 55.99
Amount available for future repurchases						$ 9,100
Subsequent Events | Revolving credit facility | United States
Subsequent Events
Borrowings under revolving line of credit			$ 13,000
Period of the borrowing is expected to be repaid		12 months	12 months
Subsequent Events | Revolving credit facility | United Kingdom
Subsequent Events
Borrowings under revolving line of credit | £		£ 5.0
Period of the borrowing is expected to be repaid		12 months	12 months