Stock-Based Compensation (Stock Option Activity) (Details) - Stock Options shares in Thousands	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Number of Shares
Options outstanding at the beginning of the period (in shares) | shares	3,606
Options granted (in shares) | shares	727
Options exercised (in shares) | shares	(569)
Options forfeited (in shares) | shares	(72)
Options expired (in shares) | shares	(4)
Options outstanding at the end of the period (in shares) | shares	3,688
Exercisable at the end of the period (in shares) | shares	2,479
Vested and expected to vest at the end of the period (in shares) | shares	3,604
Weighted-Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 25.07
Options granted (in dollars per share) | $ / shares	28.09
Options exercised (in dollars per share) | $ / shares	20.95
Options forfeited (in dollars per share) | $ / shares	28.12
Options expired (in dollars per share) | $ / shares	20.08
Options outstanding at the end of the period (in dollars per share) | $ / shares	26.24
Exercisable at the end of the period (in dollars per share) | $ / shares	25.33
Vested and expected to vest at the end of the period (in dollars per share) | $ / shares	$ 26.20