Net Income Per Share Reconciliation of Weighted Average Common Shares Outstanding (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding (basic) (in shares)	174,991	173,020	174,582	173,248
Impact of common stock equivalents (in shares)	1,225	1,044	1,194	1,017
Weighted average shares outstanding (diluted) (in shares)	176,216	174,064	175,776	174,265