Common Equity (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013
Stock options outstanding
Options Outstanding, Number, Total	8,089,710
Options Outstanding, Weighted-Average Exercise Price	$ 26.84
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	5 years 5 months
Options Exercisable, Number, Total	5,708,920
Options Exercisable, Weighted-Average Exercise Price	$ 23.16
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	4 years 1 month
Exercise Price, Range One [Member]
Stock options outstanding
Options Outstanding, Number, Total	2,128,370
Options Outstanding, Weighted-Average Exercise Price	$ 20.34
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	3 years 11 months
Options Exercisable, Number, Total	2,128,370
Options Exercisable, Weighted-Average Exercise Price	$ 20.34
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	3 years 11 months
Exercise Price, Range One [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 21.11
Exercise Price, Range One [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 16.72
Exercise Price, Range Two [Member]
Stock options outstanding
Options Outstanding, Number, Total	3,689,900
Options Outstanding, Weighted-Average Exercise Price	$ 24.65
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	4 years 2 months
Options Exercisable, Number, Total	3,382,630
Options Exercisable, Weighted-Average Exercise Price	$ 24.23
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	4 years 0 months
Exercise Price, Range Two [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 29.35
Exercise Price, Range Two [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 23.88
Exercise Price, Range Three [Member]
Stock options outstanding
Options Outstanding, Number, Total	2,271,440
Options Outstanding, Weighted-Average Exercise Price	$ 36.48
Options Outstanding, Weighted-Average Remaining Contractual Life (Years)	8 years 7 months
Options Exercisable, Number, Total	197,920
Options Exercisable, Weighted-Average Exercise Price	$ 35.19
Options Exercisable, Weighted-Average Remaining Contractual Life (Years)	8 years 1 month
Exercise Price, Range Three [Member] | Maximum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 37.46
Exercise Price, Range Three [Member] | Minimum [Member]
Stock options outstanding
Options Outstanding, Weighted-Average Exercise Price	$ 34.88