Capital Structure - Additional Information (Details)			3 Months Ended		9 Months Ended
	Feb. 28, 2017 USD ($)	Dec. 30, 2014 USD ($)	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) ClassOfCommonStock $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares
Equity, Class of Treasury Stock [Line Items]
Number of classes of common stock outstanding | ClassOfCommonStock					1
Acquisition of restricted stock from employees in connection with withholding tax payments (in shares) | shares			0	0	65,003	16,027
Withholding tax payments related to the vesting of restricted stock for total consideration					$ 3,016,000	$ 728,000
Weighted average purchase price prior to the vesting date (in dollars per share) | $ / shares					$ 46.40	$ 45.44
2014 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, period start (year)		2015
Stock repurchase program, period end (year)		2017
Repurchase of common stock authorized by board of directors up to		$ 20,000,000
Common stock shares purchased under the repurchase program (in shares) | shares				108,143		302,953
Common stock aggregate purchase price including commissions				$ 5,466,000		$ 14,441,000
Common stock average purchase price per share (in dollars per share) | $ / shares				$ 50.54		$ 47.67
2017 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, period start (year)	2017
Stock repurchase program, period end (year)	2019
Additional authorized amount	$ 100,000,000
Authorized increase in repurchase amount, 2018	40,000,000
Authorized increase in repurchase amount, 2019	40,000,000
2017 Repurchase Program | Minimum
Equity, Class of Treasury Stock [Line Items]
Authorized increase in repurchase amount	20,000,000
2017 Repurchase Program | Maximum
Equity, Class of Treasury Stock [Line Items]
Authorized increase in repurchase amount	$ 40,000,000
2014 and 2017 Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Common stock shares purchased under the repurchase program (in shares) | shares			160,033		584,017
Common stock aggregate purchase price including commissions			$ 9,004,000		$ 29,320,000
Common stock average purchase price per share (in dollars per share) | $ / shares			$ 56.26		$ 50.20