Equity Compensation - Stock Options Outstanding by Exercise Price (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 21.22	$ 22.74	$ 23.86	$ 26.21
Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per shares)	13.37	13.37	13.35
Exercise price range, upper limit (in dollars per shares)	$ 33.36	$ 47.80	$ 47.80
Options Outstanding - Number Outstanding at end of period (in shares)	2,942,783
Options Outstanding - Weighted Average Remaining Contractual Life	4 years 3 months
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 21.22
Options Exercisable - Number Exercisable at end of period (in shares)		2,656,983
Options Exercisable - Weighted Average Exercise Price (in dollars per share)		$ 21.98
Stock Options | $ 13.37 – $20.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per shares)	13.37
Exercise price range, upper limit (in dollars per shares)	$ 20
Options Outstanding - Number Outstanding at end of period (in shares)	778,159
Options Outstanding - Weighted Average Remaining Contractual Life	6 years 8 months
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 14.12
Options Exercisable - Number Exercisable at end of period (in shares)		493,671
Options Exercisable - Weighted Average Exercise Price (in dollars per share)		$ 14.11
Stock Options | $ 20.01 – $25.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per shares)	20.01
Exercise price range, upper limit (in dollars per shares)	$ 25.00
Options Outstanding - Number Outstanding at end of period (in shares)	1,353,578
Options Outstanding - Weighted Average Remaining Contractual Life	3 years 3 months
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 22.59
Options Exercisable - Number Exercisable at end of period (in shares)		1,353,578
Options Exercisable - Weighted Average Exercise Price (in dollars per share)		$ 22.59
Stock Options | $ 25.01 – $30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per shares)	25.01
Exercise price range, upper limit (in dollars per shares)	$ 30
Options Outstanding - Number Outstanding at end of period (in shares)	783,738
Options Outstanding - Weighted Average Remaining Contractual Life	3 years 8 months
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 25.55
Options Exercisable - Number Exercisable at end of period (in shares)		783,738
Options Exercisable - Weighted Average Exercise Price (in dollars per share)		$ 25.55
Stock Options | $ 30.01 – $33.36
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower limit (in dollars per shares)	30.01
Exercise price range, upper limit (in dollars per shares)	$ 33.36
Options Outstanding - Number Outstanding at end of period (in shares)	27,308
Options Outstanding - Weighted Average Remaining Contractual Life	1 year
Options Outstanding - Weighted Average Exercise Price (in dollars per share)	$ 31.74
Options Exercisable - Number Exercisable at end of period (in shares)		25,996
Options Exercisable - Weighted Average Exercise Price (in dollars per share)		$ 31.73