Equity-Based Compensation - (Details) - USD ($)		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Employee stock-based compensation expense
Equity-based compensation expense		$ 562,000	$ 766,000
Tax benefit from share-based compensation		(123,000)	(170,000)
Excess tax benefit from share-based compensation		(207,000)
Net compensation cost		232,000	596,000
Time-based Restricted Stock Units
Employee stock-based compensation expense
Equity-based compensation expense		$ 527,000	$ 766,000
Restricted Stock Units
Nonvested at beginning of period		127,011
Granted		43,450
Shares vested (including tax withholding)	[1]	(30,881)
Forfeited		(7,828)
Nonvested at end of period		131,752
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]	33.36
Forfeited, Weighted average grant date fair value per share		33.18
Nonvested at end of period, Weighted average grant date fair value per share		$ 40.31
Unrecognized compensation cost		$ 4,484,000
Period for recognition of RSU compensation expense		1 year 11 months 19 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		$ 35,000
Restricted Stock Units
Granted	[2]	33,961
Nonvested at end of period		33,961
Granted, Weighted average grant date fair value per share	[2]	$ 57.88
Nonvested at end of period, Weighted average grant date fair value per share		$ 57.88
Period of performance measurement		3 years
Unrecognized compensation cost		$ 1,341,000
Period for recognition of RSU compensation expense		2 years 9 months
Additional shares available to grant under plan (in shares)		2,385,336
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.