Employee Benefit Plans - Awards Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2013
Stock Options
Summary of options issued and outstanding
Balance at the beginning of the period (in shares)	4,229,555
Options granted (in shares)	102,355
Options exercised (in shares)	(1,199,339)
Options forfeited/expired (in shares)	(3,320)
Balance at the end of the period (in shares)	3,129,251
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 20.10
Options granted (in dollars per share)	$ 19.36
Options exercised (in dollars per share)	$ 17.75
Options forfeited (in dollars per share)	$ 24.21
Balance at the end of the period (in dollars per share)	$ 20.97
Weighted Average Grant Date Fair Value (in dollars per share)	$ 8.94
Number of Exercisable Options at the beginning of the period (in shares)	4,047,374
Number of Exercisable Options at the end of the period (in shares)	2,987,088
Performance Stock Options
Summary of options issued and outstanding
Balance at the beginning of the period (in shares)	293,077
Options granted (in shares)	72,640
Options exercised (in shares)	0
Options forfeited/expired (in shares)	0
Balance at the end of the period (in shares)	365,717
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 17.44
Options granted (in dollars per share)	$ 19.24
Options exercised (in dollars per share)	$ 0.00
Options forfeited (in dollars per share)	$ 0.00
Balance at the end of the period (in dollars per share)	$ 17.80
Weighted Average Grant Date Fair Value (in dollars per share)	$ 8.17
Number of Exercisable Options at the beginning of the period (in shares)	0
Number of Exercisable Options at the end of the period (in shares)	0
Restricted Stock Awards
Restricted Stock Award and Restricted Stock Unit Activity
Nonvested at the beginning of the period (in shares)	88,549
Granted (in shares)	48,273
Vested (in shares)	(88,549)
Forfeited (in shares)	0
Nonvested at the end of the period (in shares)	48,273
Weighted Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 12.93
Granted (in dollars per share)	$ 23.20
Vested (in dollars per share)	$ 12.93
Forfeited (in dollars per share)	$ 0.00
Nonvested at the end of the period (in dollars per share)	$ 23.20
Restricted Stock Units
Restricted Stock Award and Restricted Stock Unit Activity
Nonvested at the beginning of the period (in shares)	1,006,411
Granted (in shares)	93,580
Delivered (in shares)	(361,157)
Forfeited (in shares)	(2,425)
Nonvested at the end of the period (in shares)	736,409
Weighted Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 16.78
Granted (in dollars per share)	$ 19.29
Delivered (in dollars per share)	$ 15.04
Forfeited (in dollars per share)	$ 17.85
Nonvested at the end of the period (in dollars per share)	$ 17.63
Performance Restricted Stock Units
Restricted Stock Award and Restricted Stock Unit Activity
Nonvested at the beginning of the period (in shares)	178,970
Granted (in shares)	44,440
Delivered (in shares)	0
Forfeited (in shares)	0
Nonvested at the end of the period (in shares)	223,410
Weighted Average Grant-Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 27.35
Granted (in dollars per share)	$ 29.54
Delivered (in dollars per share)	$ 0
Forfeited (in dollars per share)	$ 0
Nonvested at the end of the period (in dollars per share)	$ 27.79