Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income		$ 21,077	$ 16,050	$ 58,243	$ 46,245
Other comprehensive income:
Unrealized (loss)/gain on effective cash flow hedges, net of taxes ($162), $1,067, $2,874 and $1,094, respectively		(557)	2,540	5,900	3,066
Foreign currency translation adjustment		(3,030)	1,716	10,813	(2,652)
Retirement benefits, net of taxes nil, $4, nil and $24, respectively		0	104	0	409
Reclassification adjustments
Realized gain on cash flow hedges, net of taxes ($129), ($205), ($476) and ($386), respectively(1)	[1]	(294)	(261)	(1,081)	(486)
Retirement benefits, net of taxes $30, $1, $77 and $3, respectively(2)	[2]	42	22	135	64
Total other comprehensive income/(loss)		(3,839)	4,121	15,767	401
Total comprehensive income		$ 17,238	$ 20,171	$ 74,010	$ 46,646

[1] These are reclassified to net income and are included in the foreign exchange gain in the unaudited consolidated statements of income. See Note 13 to the unaudited consolidated financial statements.

[2] These are reclassified to net income and are included in the computation of net periodic pension costs in the unaudited consolidated statements of income. See Note 16 to the unaudited consolidated financial statements.