Unaudited Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income		$ 20,378	$ 16,375	$ 37,166	$ 30,195
Other comprehensive income:
Unrealized (loss)/gain on effective cash flow hedges, net of taxes $1,085, ($376), $3,036 and $27, respectively		(315)	(1,508)	6,457	526
Foreign currency translation adjustment		2,200	(5,401)	13,843	(4,368)
Retirement benefits, net of taxes nil, $15, nil and $20, respectively		0	123	0	305
Reclassification adjustments
Realized gain on cash flow hedges, net of taxes ($156), ($156), ($347) and ($181), respectively(1)	[1]	(354)	(193)	(787)	(225)
Retirement benefits, net of taxes $40, $1, $47 and $2, respectively(2)	[2]	31	21	93	42
Total other comprehensive income/(loss)		1,562	(6,958)	19,606	(3,720)
Total comprehensive income		$ 21,940	$ 9,417	$ 56,772	$ 26,475

[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