Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Summary of Remediation Reserve Activity

A roll forward of remediation reserves on the balance sheet is comprised of the following:

	Years Ended December 31,
	2016			2015			2014
Balance at beginning of period	$	20,603		$	3,918		$	5,116
Remediation expense	556			18,591			1,521
Remediation payments	(2,983		)	(1,906		)	(2,719		)
Balance at end of the period	$	18,176		$	20,603		$	3,918