Stock-Based Compensation (Nonvested Performance-based Award Activity) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Non-vested PVS Awards, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, Beginning (in usd per share)	$ 23.86	$ 20.98	$ 19.65
Granted at target level	$ 47.34	$ 29.56	$ 21.22
Adjustments above/(below) target	$ 22.72	$ 25.30	$ 15.22
Vested and converted	$ 47.34	$ 29.56	$ 21.22
Outstanding, Ending (in usd per share)	$ 26.15	$ 23.86	$ 20.98
Incentive Stock Awards [Member]
Non-vested PVS Awards [Roll Forward]
Granted at target level	4,200	5,300	2,800
Forfeited	(4,100)	(200)	(800)
Non-vested PVS Awards, Weighted Average Grant Date Fair Value [Roll Forward]
Granted at target level	$ 48.69	$ 29.56	$ 21.22
Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares to be issued upon conversion	606,198
Average remaining term of shares issued at conversion	1 year
Non-vested PVS Awards [Roll Forward]
Outstanding, Beginning	578,358	652,662	657,038
Granted at target level	133,823	175,498	209,680
Adjustments above/(below) target	53,438	38,330	(120,155)
Vested and converted	(250,205)	(273,044)	(83,859)
Forfeited	(44,695)	(15,088)	(10,042)
Outstanding, Ending	470,719	578,358	652,662
Non-vested PVS Awards, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, Beginning (in usd per share)	$ 23.79	$ 21.42	$ 19.39
Granted at target level	$ 47.21	$ 29.67	$ 21.33
Adjustments above/(below) target	$ 22.86	$ 23.83	$ 13.86
Vested and converted	$ 48.69	$ 29.56	$ 21.22
Forfeited	$ 30.76	$ 23.29	$ 20.98
Outstanding, Ending (in usd per share)	$ 30.93	$ 23.79	$ 21.42
Performance-Vesting Units [Member]
Non-vested PVS Awards [Roll Forward]
Outstanding, Beginning	79,456	69,240	54,572
Granted at target level	1,584	25,538	27,100
Adjustments above/(below) target	6,907	3,000	(7,156)
Vested and converted	(32,438)	(18,322)	(5,276)
Outstanding, Ending	55,509	79,456	69,240
Minimum [Member] \| Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	0.00%
Minimum [Member] \| Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	0.00%
Maximum [Member] \| Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	200.00%
Maximum [Member] \| Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Actual payout range	200.00%

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

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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- Definition

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

-Publisher FASB

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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

-Publisher FASB

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-SubTopic 10

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- Definition

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

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

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

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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

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

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

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Weighted average remaining contractual term for equity-based awards excluding options, 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

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

-Paragraph 2

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

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

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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.

+ References

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

-Publisher FASB

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Share-based Compensation Arrangement by Share-based Payment Award, Actual Payout, Percentage

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Adjustments Above (Below) Target

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Adjustments Above (Below) Target, Weighted Average Grant Date Fair Value

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Expected to Vest, Number of Shares Issuable Upon Vesting

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