Share-Based Compensation (Details 1) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Restricted Stock Units (RSUs) [Member]
Summary of restricted stock award activity
Nonvested, Beginning of Period	287,375
Granted	218,017
Vested	(3,261)
Forfeited	(5,025)
Nonvested, End of Period	497,106
Weighted Average Grant-Date Fair Value, Beginning of Period	19.50
Weighted Average Grant-Date Fair Value, Granted	19.48
Weighted Average Grant Date Fair Value, Vested	23.56
Weighted Average Grant Date Fair Value, Forfeited	21.40
Weighted Average Grant-Date Fair Value, End of Period	19.44
Restricted Stock [Member]
Summary of restricted stock award activity
Nonvested, Beginning of Period	2,493,046
Granted	1,331,077
Vested	(425,116)
Forfeited	(211,416)
Nonvested, End of Period	3,187,591
Weighted Average Grant-Date Fair Value, Beginning of Period	34.60
Weighted Average Grant-Date Fair Value, Granted	19.19
Weighted Average Grant Date Fair Value, Vested	57.59
Weighted Average Grant Date Fair Value, Forfeited	25.13
Weighted Average Grant-Date Fair Value, End of Period	25.63
Performance unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 6 months	1 year 7 months 6 days
Summary of restricted stock award activity
Nonvested, Beginning of Period	463,317
Granted	644,412
Vested	(150,769)
Forfeited	(206,808)
Nonvested, End of Period	750,152	463,317

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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