Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Average Estimated Useful Lives of Property Plant and Equipment

The following table sets forth the average estimated useful lives at acquisition of the Company’s property, plant and equipment, by asset category:

Asset category	Depreciable Life (years)
Buildings	30 - 50
Building and leasehold improvements	10 - 20
Furniture and equipment	7 - 20
Automobiles	5 - 7
Computer hardware and software	3 - 5

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table summarizes the basis used to measure the fair values of the Company’s financial instruments (amounts in thousands):

			Fair Value Measurements at Reporting Date, Using:
Description	December 31, 2017		Quoted Prices in Active Markets for Identical Items (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and cash equivalents	$	368,119	$	368,119	$	—	$	—
Available-for-sale securities	35		—		—		35
Total assets	$	368,154	$	368,119	$	—	$	35
Purchase consideration payable	$	3,901	$	—	$	—	$	3,901
Total liabilities	$	3,901	$	—	$	—	$	3,901

Description	December 31, 2016		Quoted Prices in Active Markets for Identical Items (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and cash equivalents	$	200,772	$	200,772	$	—	$	—
Available-for-sale securities	1,106		1,074		—		32
Total assets	$	201,878	$	201,846	$	—	$	32
Purchase consideration payable	$	4,994	$	—	$	—	$	4,994
Total liabilities	$	4,994	$	—	$	—	$	4,994