Acquisitions (Details) - USD ($) $ in Thousands				1 Months Ended	12 Months Ended
	Oct. 20, 2016	Aug. 17, 2015	Oct. 01, 2014	Jan. 31, 2017	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Business Acquisition
Purchase price allocation, goodwill					$ 49,314	$ 47,700	$ 47,978
Nice Instruments
Business Acquisition
Total purchase consideration	$ 2,000
Purchase price allocation, inventory and equipment					15
Purchase price allocation, intangibles					700
Purchase price allocation, goodwill					$ 1,300
National Meter and Automation, Inc.
Business Acquisition
Total purchase consideration			$ 22,900
Cash payment			$ 20,300
Purchase price allocation, goodwill						3,000
Outstanding common stock acquired (as a percent)			100.00%
Incremental annual revenues			$ 15,000
Deferred payments						2,500
Receivables						3,900
Inventory						4,500
Property, plant and equipment						2,800
Intangibles						9,800
Current liabilities						100
Transaction costs						400
Accounts Payable | National Meter and Automation, Inc.
Business Acquisition
Deferred payments						2,000
Long-term Debt | National Meter and Automation, Inc.
Business Acquisition
Deferred payments						$ 500
Customer technology | Nice Instruments
Business Acquisition
Estimated average useful life					15 years
Customer relationships | National Meter and Automation, Inc.
Business Acquisition
Estimated average useful life					12 years
National Meter and Automation, Inc. | United Utilities, Inc.
Business Acquisition
Total purchase consideration		$ 3,300
Cash payment		400
Purchase price allocation, goodwill							300
Receivables		$ 2,900
Receivables							800
Inventory							400
Property, plant and equipment							100
Intangibles							$ 1,700
National Meter and Automation, Inc. | Customer relationships | United Utilities, Inc.
Business Acquisition
Estimated average useful life					12 years
Subsequent Event | Nice Instruments
Business Acquisition
Cash payment				$ 200