Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Reconciliation of Weighted Average Common Shares Outstanding

A reconciliation of weighted average common shares outstanding used to calculate basic and diluted net income per share follows:

	2017	2016	2015
	(in thousands)
Weighted average common shares outstanding (basic)	174,721	173,325	175,721
Impact of common stock equivalents	1,211	1,093	1,053
Weighted average common shares outstanding (diluted)	175,932	174,418	176,774