Stock-Based Compensation - Restricted Stock (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock expense	$ 26.7	$ 28.0	$ 20.7
Restricted stock expense, net of tax	$ 19.5	$ 20.4	$ 15.1
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, beginning balance	1,326,000	1,266,000	1,411,000
Nonvested shares subject to restriction, weighted average price, beginning balance	$ 53.18	$ 43.57	$ 37.86
Nonvested shares subject to restriction, granted	724,000	687,000	447,000
Nonvested shares subject to restriction, weighted average price, granted	$ 30.07	$ 58.45	$ 54.36
Nonvested shares subject to restriction, vested	(551,000)	(588,000)	(530,000)
Nonvested shares subject to restriction, weighted average price, vested	$ 47.55	$ 39.14	$ 37.42
Nonvested shares subject to restriction, forfeited	(70,000)	(39,000)	(62,000)
Nonvested shares subject to restriction, weighted average price, forfeited	$ 43.05	$ 50.85	$ 41.14
Nonvested shares subject to restriction, ending balance	1,429,000	1,326,000	1,266,000
Nonvested shares subject to restriction, weighted average price, ending balance	$ 44.12	$ 53.18	$ 43.57
Restricted stock unrecognized compensation, amount	$ 25.6
Restricted stock unrecognized compensation, period	2 years
Management [Member]
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, granted	698,788
Director [Member]
Status of nonvested restricted stock [Roll Forward]
Nonvested shares subject to restriction, granted	25,048