Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Options Roll Forward
Shares outstanding under option, Beginning Balance	473,000
Weighted average exercise price, Beginning Balance	$ 17.47
Shares outstanding under option, Exercised	(473,000)
Shares outstanding under option, Exercised, Weighted average exercise price	$ 17.47
Shares outstanding under option, Ending Balance	0		473,000
Weighted average exercise price, Ending Balance			$ 17.47
Weighted average remaining contractual term			1 month
Aggregate intrinsic value, outstanding			$ 10.4
Status of nonvested restricted stock
Nonvested shares subject to restriction, Beginning Balance	1,429,000
Nonvested shares subject to restriction, weighted average exercise price	$ 44.12
Restricted shares granted to employees	777,000
Granted shares subject to restriction, weighted average exercise price	$ 40.07
Shares subject to restriction, Vested	(453,000)
Vested shares subject to restriction, weighted average exercise price	$ 57.35
Shares subject to restriction, Forfeited	(28,000)
Forfeited shares subject to restriction, weighted average exercise price	$ 41.87
Nonvested shares subject to restriction, Ending Balance	1,725,000		1,429,000
Nonvested shares subject to restriction, weighted average exercise price	$ 39.27		$ 44.12
Restricted Stock [Member]
Restricted stock compensation expense
Restricted stock compensation expense	$ 6.8	$ 6.4
Status of nonvested restricted stock
Restricted shares granted to employees	776,753
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 47.0
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 3 months
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share compensation expense	$ 3.1	$ 3.0
Relative Revenue Growth Performance Share Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance share compensation expense	$ 3.2
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	4,800,000
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