Property, Plant and Equipment (Tables)

12 Months Ended

Mar. 31, 2019

The following table summarizes the activity in the liability for asset retirement obligations.



	Asset Retirement Obligations
Balance at March 31, 2017	$	9,953
Liabilities incurred during the period	89
Liabilities settled during the period	(352		)
Accretion expense	1,198
Foreign currency and other	751
Balance at March 31, 2018	$	11,639
Liabilities incurred during the period	1,033
Accretion expense	385
Foreign currency and other	(671		)
Balance at March 31, 2019	$	12,386

Future minimum annual rentals payable under noncancelable operating lease agreements at March 31, 2019 were as follows:



	Operating Leases
2020	$	24,008
2021	18,567
2022	13,917
2023	11,929
2024 and thereafter	93,939
Total minimum lease payments	$	162,360

We generally depreciate or deplete property, plant, and equipment over the useful lives presented in the following table:



Asset Type		Useful Life (years)
Land improvements		3-40
Buildings and leasehold improvements		2-50
Machinery and equipment		2-20
Information Systems		2-20
Radioisotope (cobalt-60)		20

Information related to the major categories of our depreciable assets is as follows:



March 31,	2019			2018
Land and land improvements ⁽¹⁾	$	63,522		$	55,417
Buildings and leasehold improvements	480,359			467,063
Machinery and equipment	656,956			631,623
Information systems	169,711			151,360
Radioisotope	483,080			458,440
Construction in progress ⁽¹⁾	133,689			87,745
Total property, plant, and equipment	1,987,317			1,851,648
Less: accumulated depreciation and depletion	(955,735		)	(841,124		)
Property, plant, and equipment, net	$	1,031,582		$	1,010,524

⁽¹⁾ Land is not depreciated. Construction in progress is not depreciated until placed in service.