Common Stock Options and Restricted Stock - Schedule of Stock Options Activity, By Exercise Price Range (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Options Outstanding
Outstanding ending balance (in shares) | shares	8,929
Weighted-average remaining contractual life	6 years
Weighted-average exercise price (in dollars per share)	$ 29.46
Options Exercisable
Exercisable ending balance (in shares) | shares	6,646
Weighted-average exercise price (In dollars per share)	$ 30.26
Range $13.80 - $22.06
Range of Exercise Price
Stock option, exercise price range, lower limit (in dollars per share)	13.80
Stock option, exercise price range, upper limit (in dollars per share)	$ 22.06
Options Outstanding
Outstanding ending balance (in shares) | shares	1,876
Weighted-average remaining contractual life	6 years
Weighted-average exercise price (in dollars per share)	$ 18.61
Options Exercisable
Exercisable ending balance (in shares) | shares	1,168
Weighted-average exercise price (In dollars per share)	$ 19.67
Range $22.13 - $28.12
Range of Exercise Price
Stock option, exercise price range, lower limit (in dollars per share)	22.13
Stock option, exercise price range, upper limit (in dollars per share)	$ 28.12
Options Outstanding
Outstanding ending balance (in shares) | shares	1,875
Weighted-average remaining contractual life	6 years 1 month 6 days
Weighted-average exercise price (in dollars per share)	$ 26.43
Options Exercisable
Exercisable ending balance (in shares) | shares	1,263
Weighted-average exercise price (In dollars per share)	$ 26.23
Range $28.14 - $32.55
Range of Exercise Price
Stock option, exercise price range, lower limit (in dollars per share)	28.14
Stock option, exercise price range, upper limit (in dollars per share)	$ 32.55
Options Outstanding
Outstanding ending balance (in shares) | shares	1,860
Weighted-average remaining contractual life	5 years 4 months 24 days
Weighted-average exercise price (in dollars per share)	$ 30.69
Options Exercisable
Exercisable ending balance (in shares) | shares	1,659
Weighted-average exercise price (In dollars per share)	$ 30.79
Range $32.56 - $35.74
Range of Exercise Price
Stock option, exercise price range, lower limit (in dollars per share)	32.56
Stock option, exercise price range, upper limit (in dollars per share)	$ 32.56
Options Outstanding
Outstanding ending balance (in shares) | shares	2,101
Weighted-average remaining contractual life	6 years 3 months 18 days
Weighted-average exercise price (in dollars per share)	$ 35.22
Options Exercisable
Exercisable ending balance (in shares) | shares	1,489
Weighted-average exercise price (In dollars per share)	$ 35.08
Range $35.84 - $44.50
Range of Exercise Price
Stock option, exercise price range, lower limit (in dollars per share)	35.84
Stock option, exercise price range, upper limit (in dollars per share)	$ 44.50
Options Outstanding
Outstanding ending balance (in shares) | shares	1,217
Weighted-average remaining contractual life	6 years 1 month 6 days
Weighted-average exercise price (in dollars per share)	$ 39.01
Options Exercisable
Exercisable ending balance (in shares) | shares	1,067
Weighted-average exercise price (In dollars per share)	$ 39.07