Stock-Based Compensation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock options additional disclosures [Abstract]
Stock-based compensation expense	$ 4,086,000	$ 3,521,000	$ 4,305,000
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Number of shares available for future grant (in shares)	3,500,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	4 years
Stock awards termination period	10 years
Stock options [Roll Forward]
Outstanding, beginning of period (in shares)	1,038,342
Granted (in shares)	36,316
Exercised (in shares)	(519,947)
Forfeited (in shares)	0
Expired (in shares)	(13,147)
Outstanding, end of period (in shares)	541,564	1,038,342
Exercisable, end of period (in shares)	501,952
Expected to vest (in shares)	39,240
Stock options, weighted average exercise price [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 23.10
Granted (in dollars per share)	25.85
Exercised (in dollars per share)	23.16
Forfeited (in dollars per share)	0
Expired (in dollars per share)	22.97
Outstanding, end of period (in dollars per share)	23.23	$ 23.10
Exercisable, end of period (in dollars per share)	23.03
Expected to vest (in dollars per share)	$ 25.76
Stock options additional disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period	3 years 2 months 26 days
Weighted average remaining contractual term, exercisable, end of period	2 years 9 months 7 days
Weighted average remaining contractual term, expected to vest	9 years 1 month 10 days
Aggregate intrinsic value, outstanding, end of period	$ 2,541,332
Aggregate intrinsic value, exercisable, end of period	2,457,469
Aggregate intrinsic value, expected to vest	83,294
Stock-based compensation expense	200,000	$ 100,000	200,000
Proceeds from stock options exercised	12,044,000	6,554,000	7,927,000
Tax (expense) benefits related to stock options exercised	(43,000)	313,000	178,000
Intrinsic value of stock options exercised	2,446,000	789,000	905,000
Fair value of shares vested during the year	63,000	$ 393,000	766,000
Restricted Stock [Member]
Stock options additional disclosures [Abstract]
Unrecognized compensation cost	$ 3,700,000
Unrecognized compensation cost, weighted average period of recognition	1 year 8 months 12 days
Restricted stock and restricted stock units [Roll Forward]
Unvested, beginning of period (in shares)	52,000
Forfeited (in shares)	0
Vested (in shares)	(29,000)
Unvested, end of period (in shares)	23,000	52,000
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 23.43
Forfeited (in dollars per share)	0
Vested (in dollars per share)	22.85
Unvested, end of period (in dollars per share)	$ 24.17	$ 23.43
Restricted Stock [Member] | Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	5 years
Restricted Stock [Member] | Non-employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	3 years
Restricted Stock Units (RSUs) [Member]
Restricted stock and restricted stock units [Roll Forward]
Unvested, beginning of period (in shares)	638,975
Forfeited (in shares)	(8,407)
Vested (in shares)	(125,520)
Granted (in shares)	160,040
Unvested, end of period (in shares)	665,088	638,975
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 31.01
Forfeited (in dollars per share)	0
Vested (in dollars per share)	0
Granted (in dollars per share)	24.67
Unvested, end of period (in dollars per share)	$ 35.73	$ 31.01
Restricted and Deferred Stock Awards [Member]
Stock options additional disclosures [Abstract]
Stock-based compensation expense	$ 4,200,000	$ 4,200,000	3,800,000
Tax benefit from compensation expense	$ 3,900,000	$ 2,900,000	$ 2,400,000