Share-Based Compensation - Performance Shares Activity (Details) - Performance shares - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Weighted Number of Shares
Nonvested at beginning of period (in shares)	203,000
Granted (in shares)	147,000
Vested (in shares)	(89,040)
Forfeited (in shares)	(39,000)
Nonvested at end of period (in shares)	222,000	203,000
Weighted Average Grant Date Fair Value
Nonvested at January 1 (in dollars per share)	$ 42.82
Granted (in dollars per share)	30.63	$ 46.46	$ 38.89
Vested (in dollars per share)	38.89
Forfeited (in dollars per share)	24.12
Nonvested at December 31 (in dollars per share)	$ 37.20	$ 42.82