Share-Based Compensation (Stock Option Activity) (Details) - $ / shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted- average grant date fair value per share
Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 9.94	$ 6.15	$ 8.40
Stock Options \| Non-vested stock options outstanding
Number of options
Beginning balance, Number of Options	407,939	479,755	432,199
Granted, Number of Options	132,414	441,167	244,165
Acquired, Number of Options		0	0
Exercised, Number of Options	0	0	0
Vested, Number of Options	(161,751)	(454,360)	(150,224)
Forfeited/expired, Number of Options	(47,732)	(58,623)	(46,385)
Ending balance, Number of Options	330,870	407,939	479,755
Weighted- average exercise price per share
Beginning balance, Weighted Average Exercise Price Per Share (USD per share)	$ 32.81	$ 28.75	$ 26.75
Granted, Weighted Average Exercise Price Per Share (USD per share)	53.43	32.81	30.18
Acquired, Weighted Average Exercise Price Per Share (USD per share)		0.00	0.00
Exercised, Weighted Average Exercise Price Per Share (USD per share)	0.00	0.00	0.00
Vested, Weighted Average Exercise Price Per Share (USD per share)	37.73	28.74	25.57
Forfeited/expired, Weighted Average Exercise Price Per Share (USD per share)	37.55	31.10	27.99
Ending balance, Weighted Average Exercise Price Per Share (USD per share)	37.97	32.81	28.75
Weighted- average grant date fair value per share
Beginning balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	6.15	8.49	8.30
Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	9.94	6.15	8.40
Acquired, Weighted Average Grant Date Fair Value Per Share (USD per share)		0.00	0.00
Exercised, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	0.00	0.00	0.00
Vested, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	7.07	8.49	7.80
Forfeited/expired, Granted, Weighted Average Grant Date Fair Value Per Share (USD per share)	7.03	7.17	8.50
Ending balance, Weighted Average Grant Date Fair Value Per Share (USD per share)	$ 7.09	$ 6.15	$ 8.49
Stock Options \| Stock options outstanding
Number of options
Beginning balance, Number of Options	2,453,395	1,054,739	1,037,311
Granted, Number of Options	132,414	441,167	244,165
Acquired, Number of Options		1,466,408	132,883
Exercised, Number of Options	(1,427,159)	(450,296)	(310,985)
Vested, Number of Options	0	0	0
Forfeited/expired, Number of Options	(47,732)	(58,623)	(48,635)
Ending balance, Number of Options	1,110,918	2,453,395	1,054,739
Weighted- average exercise price per share
Beginning balance, Weighted Average Exercise Price Per Share (USD per share)	$ 21.41	$ 25.38	$ 25.90
Granted, Weighted Average Exercise Price Per Share (USD per share)	53.43	32.81	30.18
Acquired, Weighted Average Exercise Price Per Share (USD per share)		15.08	12.93
Exercised, Weighted Average Exercise Price Per Share (USD per share)	17.50	20.02	25.10
Vested, Weighted Average Exercise Price Per Share (USD per share)	0.00	0.00	0.00
Forfeited/expired, Weighted Average Exercise Price Per Share (USD per share)	37.55	31.10	28.18
Ending balance, Weighted Average Exercise Price Per Share (USD per share)	$ 29.56	$ 21.41	$ 25.38
Weighted- average grant date fair value per share
Options Exercisable, Number Exercisable (in shares)	780,048
Exercisable/vested, Weighted Average Exercise Price Per Share (USD per share)	$ 25.99

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Converted options from acquisitions, Weighted Average Exercise Price

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Converted options from acquisitions, Wtd Avg Grant Date Fair Value

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Share based compensation arrangement by share based payment award, option, vested and expected to vest, outstanding number.

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Share-based compensation arrangement by share-based payment award, options, exercises in period, weighted average grant date fair value.

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Grant Date Fair Value [Roll Forward]

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Share-based compensation arrangement by share-based payment award, options, vested in period, weighted average grant date fair value.

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Share based compensation arrangements by share based payment award, options, forfeitures and expirations in period, weighted average grant date fair value.

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Share-Based Compensation Arrangements By Share-Based Payment Award, Options, Vested In Period, Weighted Average Exercise Price

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- Definition

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

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

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Number of share options (or share units) exercised during the current period.

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