Stock-Based Compensation - Restricted Stock Awards (Details) - USD ($)		12 Months Ended
	Mar. 03, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2017	Mar. 31, 2015	Jan. 01, 2015	Mar. 31, 2012
Chairman, President, and Chief Executive Officer | Common Stock | Achieves a specified improvement in total shareholder return at the end of 2016 compared to 2011 and she remains an employee
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)								135,000
Chairman, President, and Chief Executive Officer | Common Stock | Achieves Specified Improvement In Total Shareholder Return At End Of 2014 Compared To 2011 And She Remains Employee
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)								35,000
Number of shares approved upon meeting target (in shares)					100,000
Chairman, President, and Chief Executive Officer | Common Stock | Achieves a specific performance target by the end of 2019 and she remains an employee
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)						53,859
Chairman, President, and Chief Executive Officer | Common Stock | Achieves a specific performance target by the end of 2017 and she remains an employee
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares authorized (in shares)						17,953
Executive Vice President and Chief Financial Officer | Common Stock | Achieved performance target for 2015 and 2016
Restricted Stock
Granted (in shares)	2,754
Weighted-Average Grant Date Fair Value
Granted (in dollars per share)	$ 36.30
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares approved upon meeting target (in shares)					100,000
Value of stock to be granted if performance targets are achieved							$ 100,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value (in dollars per share)	$ 36.30
Executive Vice President and Chief Financial Officer | Common Stock | Achieved performance target for 2015, 2016 and 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Value of stock to be granted if performance targets are achieved							$ 275,000
Restricted Stock
Restricted Stock
Beginning balance (in shares)		218,316
Granted (in shares)		248,271
Exercised (in shares)		(273,530)
Forfeited (in shares)		(4,012)
Ending balance (in shares)		189,045	218,316
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share)		$ 27.59
Granted (in dollars per share)		23.06	$ 26.49	$ 20.34
Exercised (in dollars per share)		21.01
Forfeited (in dollars per share)		29.96
Ending balance (in dollars per share)		31.11	27.59
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value (in dollars per share)		$ 23.06	$ 26.49	$ 20.34
Total fair value of restricted shares that vested		$ 5,747,000	$ 5,079,000	$ 6,507,000
Stock Options
Stock Options
Beginning balance (in shares)		305,874
Granted (in shares)		0
Exercised (in shares)		(109,433)
Forfeited (in shares)		0
Expired (in shares)		(3,000)
Ending balance (in shares)		193,441	305,874
Weighted Average Exercise Price
Beginning balance (in dollars per share)		$ 12.29
Granted (in dollars per share)		0.00
Exercised (in dollars per share)		15.89
Forfeited (in dollars per share)		0.00
Expired (in dollars per share)		30.50
Ending balance (in dollars per share)		$ 9.98	$ 12.29
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Aggregate intrinsic value of stock options outstanding		$ 5,900,000
Weighted average remaining contract life		1 year 6 months 18 days
Exercise price of stock options that are greater than the closing price (in shares)		0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted-average grant date fair value options granted (in dollars per share)		$ 0.00	$ 0.00	$ 0.00
Total fair value of options that vested		$ 0	$ 0	$ 0
Total intrinsic value of options exercised		$ 2,234,000	$ 1,242,000	$ 2,350,000
Performance Shares | Executive
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares granted (in shares)		49,682
Weighted percentage assigned to achieving market targets		60.00%
Weighted percentage assigned to achieving performance targets		40.00%
Shares excluded (in shares)		97,697
Shares approved, maximum number of shares available in year two (in shares)		137,036
Shares approved, maximum number of shares available in year three (in shares)		133,632
Performance period		3 years