Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Options Roll Forward
Shares outstanding under option, Beginning Balance	1,267,000
Weighted average exercise price, Beginning Balance	$ 16.59
Shares outstanding under option, Exercised	(165,000)
Shares outstanding under option, Exercised, Weighted average exercise price	$ 16.81
Shares outstanding under option, Ending Balance	1,102,000		1,267,000
Weighted average exercise price, Ending Balance	$ 16.56		$ 16.59
Weighted average remaining contractual term	8 months		11 months
Aggregate intrinsic value, outstanding	$ 24.1		$ 33.7
Status of nonvested restricted stock
Nonvested shares subject to restriction, Beginning Balance	1,326,000
Nonvested shares subject to restriction, weighted average exercise price	$ 53.18
Restricted shares granted to employees	668,000
Granted shares subject to restriction, weighted average exercise price	$ 29.61
Shares subject to restriction, Vested	(493,000)
Vested shares subject to restriction, weighted average exercise price	$ 46.06
Shares subject to restriction, Forfeited	(19,000)
Forfeited shares subject to restriction, weighted average exercise price	$ 42.84
Nonvested shares subject to restriction, Ending Balance	1,482,000		1,326,000
Nonvested shares subject to restriction, weighted average exercise price	$ 45.03		$ 53.18
Restricted Stock [Member]
Restricted stock compensation expense
Restricted stock compensation expense	$ 6.4	$ 7.3
Status of nonvested restricted stock
Restricted shares granted to employees	667,874
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 44.2
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years
Stock Incentive Plan 2004 [Member] | Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Term of award	10 years
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	5,700,000
Number of shares authorized	8,000,000
First Half Vested | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years
Percent of awards vested	50.00%
Second Half Vested | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years