Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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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).

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

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Share-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock option exercise			$ 45	$ 149
2004 Non-employee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercises in period			1,500	9,349
Proceeds from stock option exercise			$ 100
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested restricted stock (in shares)			175,746
Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares (in shares)	2,500	100,000
Weighted average grant date fair value	$ 84.18	$ 79.30
Director [Member] \| Restricted Stock [Member] \| 2004 Non-employee Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares (in shares)		15,600
Weighted average grant date fair value		$ 79.02
Award vesting percentage		100.00%
Third Anniversary \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	35.00%	20.00%
Fourth Anniversary \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	35.00%	30.00%
Fifth Anniversary \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	20.00%	35.00%
Sixth Anniversary \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	5.00%	10.00%
Seventh Anniversary \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	5.00%	5.00%
Subject to Performance Conditions Over 5 years \| Restricted Stock [Member] \| 2015 Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares (in shares)		100,000
Weighted average grant date fair value		$ 79.30