Stock-Based Compensation - Long-Term Performance-Based Plans - Additional (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Recognized non-cash stock-based compensation expense
Non-cash stock-based compensation expense recognized	$ 29,941	$ 13,037	$ 19,199
Outstanding awards pursuant to performance-based stock incentive plans
Performance Based Stock Options (in shares)	5,490,626
Weighted-Average Exercise Price (in dollars per share)	$ 42.81
Restricted Performance Units (in shares)	2,484,720	1,336,000	1,382,250	1,798,331
LTIP 2013
Recognized non-cash stock-based compensation expense
Non-cash stock-based compensation expense recognized	$ (321)	$ 2,565	$ 10,157
Estimated Remaining Non-Cash, Stock-Based Compensation Expense
Remaining expense estimated to be recognized during 2016	1,974
Estimated contingent expense subsequent to 2016	39,234
Total estimated remaining expense over the term of plan	$ 41,208
Outstanding awards pursuant to performance-based stock incentive plans
Performance Based Stock Options (in shares)	1,205,000
Weighted-Average Exercise Price (in dollars per share)	$ 41.78
LTIP 2017
Recognized non-cash stock-based compensation expense
Non-cash stock-based compensation expense recognized	$ 10,640
Estimated Remaining Non-Cash, Stock-Based Compensation Expense
Remaining expense estimated to be recognized during 2016	8,271
Estimated contingent expense subsequent to 2016	18,694
Total estimated remaining expense over the term of plan	$ 26,965
Outstanding awards pursuant to performance-based stock incentive plans
Performance Based Stock Options (in shares)	2,545,626
Weighted-Average Exercise Price (in dollars per share)	$ 59.38
Other Employee Performance Awards
Recognized non-cash stock-based compensation expense
Non-cash stock-based compensation expense recognized	$ 7,549	1,424	1,694
Estimated Remaining Non-Cash, Stock-Based Compensation Expense
Remaining expense estimated to be recognized during 2016	17,946
Estimated contingent expense subsequent to 2016	123,655
Total estimated remaining expense over the term of plan	$ 141,601
Outstanding awards pursuant to performance-based stock incentive plans
Performance Based Stock Options (in shares)	1,740,000
Weighted-Average Exercise Price (in dollars per share)	$ 19.27
Restricted Performance Units (in shares)	1,833,000
Other Employee Performance Awards | Continuing operations [Member]
Recognized non-cash stock-based compensation expense
Non-cash stock-based compensation expense recognized	$ 17,868	$ 3,989	$ 11,851
Restricted Performance Units
Outstanding awards pursuant to performance-based stock incentive plans
Performance Based Stock Options (in shares)	2,500,000
Restricted Performance Units (in shares)	2,435,500	1,336,000	1,382,250
Restricted Performance Units | LTIP 2013
Outstanding awards pursuant to performance-based stock incentive plans
Restricted Performance Units (in shares)	602,500