Stock Compensation Shares Authorized under Stock Option Plans by Exercise Price Range (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding (in shares)	3,289,802	3,304,595	2,519,918	2,544,574
Outstanding, Weighted Average Remaining Contractual Term	6 years 4 months 24 days	6 years 6 months 18 days	6 years 7 months 6 days	7 years 7 months 6 days
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 13.41	$ 12.58	$ 11.90	$ 11.89
Options exercisable (in shares)	1,522,748	1,866,016	439,277
Exercisable, Weighted-Average Remaining Contractual Life (Years)	4 years 9 months 13 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 11.10
Options Exercisable, Weighted Aggregate Intrinsic Value	$ 15,544
Exercise Price Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 0.00
Range of Exercise Prices, Maximum (in dollars per share)	$ 11.55
Options Outstanding (in shares)	1,496,029
Outstanding, Weighted Average Remaining Contractual Term	4 years 9 months 18 days
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 11.07
Options exercisable (in shares)	1,496,029
Exercisable, Weighted-Average Remaining Contractual Life (Years)	4 years 9 months 18 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 11.07
Options Exercisable, Weighted Aggregate Intrinsic Value	0
Exercise Price Range Two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 11.55
Range of Exercise Prices, Maximum (in dollars per share)	$ 13.86
Options Outstanding (in shares)	73,822
Outstanding, Weighted Average Remaining Contractual Term	5 years 4 months 24 days
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 12.98
Options exercisable (in shares)	26,719
Exercisable, Weighted-Average Remaining Contractual Life (Years)	5 years 1 month 6 days
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 13.04
Options Exercisable, Weighted Aggregate Intrinsic Value	0
Exercise Price Range Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 13.86
Range of Exercise Prices, Maximum (in dollars per share)	$ 16.17
Options Outstanding (in shares)	1,313,076
Outstanding, Weighted Average Remaining Contractual Term	7 years 4 months 24 days
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 14.47
Options exercisable (in shares)	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options Exercisable, Weighted Aggregate Intrinsic Value	0
Exercise Price Range Four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 16.17
Range of Exercise Prices, Maximum (in dollars per share)	$ 18.48
Options Outstanding (in shares)	0
Outstanding, Weighted Average Remaining Contractual Term	0 years
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options exercisable (in shares)	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options Exercisable, Weighted Aggregate Intrinsic Value	0
Exercise Price Range Five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 18.48
Range of Exercise Prices, Maximum (in dollars per share)	$ 20.79
Options Outstanding (in shares)	406,875
Outstanding, Weighted Average Remaining Contractual Term	9 years 2 months 12 days
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 18.71
Options exercisable (in shares)	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options Exercisable, Weighted Aggregate Intrinsic Value	0
Exercise Price Range Six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 20.79
Range of Exercise Prices, Maximum (in dollars per share)	$ 23.10
Options Outstanding (in shares)	0
Outstanding, Weighted Average Remaining Contractual Term	0 years
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options exercisable (in shares)	0
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 0.00
Options Exercisable, Weighted Aggregate Intrinsic Value	$ 0