Employee Compensation Plans - Stock Appreciation Rights (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	1,907,030
Total weighted average strike price (in dollars per share)	$ 21.36
Total weighted average remaining contractual life (in years)	2 years 3 months 24 days
Total weighted average fair value per share (in dollars per share)	$ 2.02
January 13, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	289,320
Strike price (in dollars per share)	$ 26.35
Remaining contractual life (in years)	12 days
Fair value per share (in dollars per share)	$ 0
January 19, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	324,710
Strike price (in dollars per share)	$ 18.94
Remaining contractual life (in years)	1 year
Fair value per share (in dollars per share)	$ 1.52
January 14, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	347,130
Strike price (in dollars per share)	$ 15.94
Remaining contractual life (in years)	2 years
Fair value per share (in dollars per share)	$ 3.45
January 14, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	442,790
Strike price (in dollars per share)	$ 23.48
Remaining contractual life (in years)	3 years
Fair value per share (in dollars per share)	$ 1.78
January 9, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding | shares	503,080
Strike price (in dollars per share)	$ 21.94
Remaining contractual life (in years)	4 years
Fair value per share (in dollars per share)	$ 2.74