Goodwill and Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2014

Changes to goodwill are as follows:



(in thousands)	Three Months Ended March 31, 2014			Year Ended December 31, 2013
Balance at beginning of period	$	1,249,316		$	813,792
Additions	—			442,170
Disposals	—			(2,834		)
Currency translation and other	(2,216		)	(3,812		)
Balance at end of period	$	1,247,100		$	1,249,316

Changes to intangible assets are as follows:



(in thousands)	Three Months Ended March 31, 2014			Year Ended December 31, 2013
Balance at beginning of period, net of accumulated amortization	$	408,923		$	125,913
Additions	—			301,800
Disposals	—			(311		)
Amortization expense	(12,441		)	(18,795		)
Currency translation and other	1,855			316
Balance at end of period, net of accumulated amortization	$	398,337		$	408,923

A summary of intangible assets follows:



	Weighted Average Amortization Period of Finite Lived Assets (in years)
		March 31, 2014						December 31, 2013
(in thousands)		Gross Asset		Accumulated Amortization		Net		Gross Asset		Accumulated Amortization		Net
Intellectual property rights	16.5	$	94,858	$	49,598	$	45,260	$	95,052	$	48,960	$	46,092
Customer relationships and backlog	13.9	422,404		96,473		325,931		420,951		86,556		334,395
Drawings	37.9	11,149		9,976		1,173		11,149		9,951		1,198
Other	12.7	64,831		38,858		25,973		64,800		37,562		27,238
Total	14.4	$	593,242	$	194,905	$	398,337	$	591,952	$	183,029	$	408,923

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.