Share-based Compensation (Summary of Information Concerning Stock Options Outstanding Including the Related Transactions under the Stock Option Plans) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares
Share-based Compensation [Abstract]
Balance, number of shares (in shares) | shares	31,507
Granted, number of shares (in shares) | shares	1,503
Exercised, number of shares (in shares) | shares	(11,914)
Forfeited and expired, number of shares (in shares) | shares	(234)
Balance, number of shares (in shares) | shares	20,862
Options Expected to Vest, number of shares (in shares) | shares	20,813
Options Exercisable, number of shares (in shares) | shares	16,139
Balance, weighted-average exercise price (in dollars per share) | $ / shares	$ 19.40
Granted, weighted-average exercise price (in dollars per share) | $ / shares	27.01
Exercised, weighted-average exercise price (in dollars per share) | $ / shares	21.39
Forfeited and expired, weighted-average exercise price (in dollars per share) | $ / shares	23.48
Balance, weighted-average exercise price (in dollars per share) | $ / shares	18.77
Options Expected to Vest, weighted-average exercise price (in dollars per share) | $ / shares	18.76
Options Exercisable, weighted-average exercise price (in dollars per share) | $ / shares	$ 17.61
Options Outstanding, weighted-average remaining contractual term in years (Year)	4 years 9 months 18 days
Options Expected to Vest, weighted-average remaining contractual term in years (Year)	4 years 9 months 15 days
Options Exercisable, weighted-average remaining contractual term in years (Year)	3 years 7 months 24 days
Options Outstanding, aggregate intrinsic value | $	$ 235,389
Options Expected to Vest, aggregate intrinsic value | $	235,075
Options Exercisable, aggregate intrinsic value | $	$ 200,826