Stock-Based Compensation (Stock Option Activity) (Details) - Stock Options shares in Thousands	6 Months Ended
	Jun. 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	684
Options exercised (in shares) | shares	(460)
Options forfeited (in shares) | shares	(19)
Options expired (in shares) | shares	(4)
Options outstanding at the end of the period (in shares) | shares	3,807
Exercisable at the end of the period (in shares) | shares	2,502
Vested and expected to vest at the end of the period (in shares) | shares	3,707
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	27.84
Options exercised (in dollars per share) | $ / shares	21.20
Options forfeited (in dollars per share) | $ / shares	28.30
Options expired (in dollars per share) | $ / shares	20.08
Options outstanding at the end of the period (in dollars per share) | $ / shares	26.02
Exercisable at the end of the period (in dollars per share) | $ / shares	24.96
Vested and expected to vest at the end of the period (in dollars per share) | $ / shares	$ 25.98