Stock-Based Compensation Plans (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Summary of stock option activities
Options exercisable (in shares)	1,077,988	1,997,969
Number of options, Beginning Balance	2,359,126
Options exercised (in shares)	(50,007)
Options forfeited (in shares)	(869,974)
Number of options, Ending Balance	1,439,145
Weighted Average Exercise Price, Beginning Balance (in dollars per share)	$ 42.59
Weighted Average Exercise Price of Options exercised (in dollars per share)	$ 21.58
Weighted Average Exercise Price of Options forfeited (in dollars per share)	$ 40.07
Weighted Average Exercise Price, Ending Balance (in dollars per share)	$ 44.83