Stock-based Compensation Stock-based Compensation (Details 6) (Restricted Stock Unit Awards, USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Outstanding, beginning of period (in shares)	2,788,000
Granted (in shares)	6,000
Vested and distributed (in shares)	(105,000)
Forfeited (in shares)	(72,000)
Outstanding, end of period (in shares)	2,617,000
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share)	$ 21.16
Granted (in dollars per share)	$ 30.27	$ 17.30
Vested and distributed (in dollars per share)	$ 25.25
Forfeited (in dollars per share)	$ 26.41
Outstanding, end of period (in dollars per share)	$ 20.88