Benefit Plans - Share Option Activity (Details) - Share Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of shares outstanding, beginning (in shares)	1,955,701	3,480,080
Number of shares exercised (in shares)		(594,791)	(1,519,179)
Number of shares forfeited (in shares)		(10,500)	(5,200)
Number of shares outstanding, ending (in shares)	1,350,410	1,955,701	3,480,080
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Price per share outstanding, beginning (in dollars per shares)	$ 6.95	$ 6.44
Price per share exercised (in dollars per shares)		6.71	$ 5.77
Exercise price per share forfeited (in dollars per shares)		7.46	7.47
Price per share outstanding, ending (in dollars per shares)	$ 7.05	$ 6.95	$ 6.44