Share-Based Compensation - Summary of Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost charged against income	$ 3,000	$ 2,300	$ 8,600	$ 6,800
Income tax benefit recognized during period	1,200	$ 892	3,400	$ 2,700
Unrecognized compensation cost	$ 20,200		$ 20,200
Weighted-average period of recognition of unrecognized compensation expense			3 years 179 days
Shares
Outstanding, beginning balance (in shares)			747,000
Granted (in shares)			228,000
Paid Out (in shares)			(216,000)
Forfeited/Canceled (in shares)			(1,000)
Outstanding, ending balance (in shares)	758,000		758,000
Grant Date Weighted- Average Fair Value Per Share
Outstanding, beginning balance (in dollars per share)			$ 37.91
Granted (in dollars per share)			56.01
Paid Out (in dollars per share)			25.81
Forfeited/Canceled (in dollars per share)			21.04
Outstanding, ending balance (in dollars per share)	$ 46.82		$ 46.82
Non-Executive Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum vesting period of outstanding options and non vested shares (in years)			4 years
Shares
Granted (in shares)			228,202
Non-Executive Employees | Anniversary One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Non-Executive Employees | Anniversary Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Non-Executive Employees | Anniversary Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Non-Executive Employees | Anniversary Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized by right	1		1
Minimum vesting period of outstanding options and non vested shares (in years)			4 years
Executive Officer | Anniversary One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Executive Officer | Anniversary Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Executive Officer | Anniversary Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%
Executive Officer | Anniversary Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage			25.00%