Equity-Based Compensation - (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employee stock-based compensation expense
Equity-based compensation expense		$ 732,000	$ 545,000	$ 1,293,000	$ 1,311,000
Tax benefit from share-based compensation		(161,000)	(120,000)	(284,000)	(288,000)
Excess tax benefit from share-based compensation		(117,000)	(201,000)	(324,000)	(201,000)
Net compensation cost		$ 454,000	224,000	$ 685,000	822,000
2013 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized		3,576,466		3,576,466
Restricted Stock Units
Additional shares available to grant under plan (in shares)		2,396,156		2,396,156
Time-based Restricted Stock Units
Employee stock-based compensation expense
Equity-based compensation expense		$ 615,000	$ 545,000	$ 1,142,000	$ 1,311,000
Restricted Stock Units
Nonvested at beginning of period				127,011
Granted				43,450
Shares vested (including tax withholding)	[1]			(58,426)
Forfeited				(2,935)
Nonvested at end of period		109,100		109,100
Nonvested at beginning of period, Weighted average grant date fair value per share				$ 33.00
Granted, Weighted average grant date fair value per share				55.45
Shares vested (including tax withholding), Weighted average grant date fair value per share	[1]			33.03
Forfeited, Weighted average grant date fair value per share				40.70
Nonvested at end of period, Weighted average grant date fair value per share		$ 41.71		$ 41.71
Unrecognized compensation cost		$ 3,688,000		$ 3,688,000
Period for recognition of RSU compensation expense				1 year 9 months 11 days
Time-based Restricted Stock Units | Directors
Restricted Stock Units
Vesting Period				1 year
Time-based Restricted Stock Units | Employees
Restricted Stock Units
Vesting Period				3 years
Performance-based Restricted Stock Units
Employee stock-based compensation expense
Equity-based compensation expense		$ 117,000		$ 151,000
Restricted Stock Units
Nonvested at beginning of period				0
Granted	[2]			33,961
Forfeited				(1,155)
Nonvested at end of period		32,806		32,806
Nonvested at beginning of period, Weighted average grant date fair value per share				$ 0.00
Granted, Weighted average grant date fair value per share	[2]			57.88
Forfeited, Weighted average grant date fair value per share				57.88
Nonvested at end of period, Weighted average grant date fair value per share		$ 57.88		$ 57.88
Period of performance measurement				3 years
Unrecognized compensation cost		$ 1,178,000		$ 1,178,000
Period for recognition of RSU compensation expense				2 years 6 months
Performance-based Restricted Stock Units | Minimum
Restricted Stock Units
Shares issued upon participants target award				0.00%
Performance-based Restricted Stock Units | Maximum
Restricted Stock Units
Shares issued upon participants target award				150.00%

[1] (a)    Pursuant to the terms of the 2013 Incentive Plan, RSUs withheld by the Company for the payment of the employee's tax withholding related to an RSU vesting are added back to the pool of shares available for future awards.

[2] (a)    Represents the total participant target award.