Stock-Based Compensation - Restricted Stock Awards (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 28, 2017	Mar. 31, 2015	Feb. 28, 2015	Jan. 01, 2015	Mar. 31, 2012
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specified improvement in total shareholder return at the end of 2016 compared to 2011 and she remains an employee [Member]
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 [Member] | Common Stock [Member] | Achieves a specified improvement in total shareholder return at the end of 2014 compared to 2011 and she remains an employee [Member]
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)						35,000
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specified improvement in total shareholder return at the end of 2014 compared to 2011 and she remains an employee [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares approved upon meeting target (in shares)				100,000
Chairman, President, and Chief Executive Officer [Member] | Common Stock [Member] | Achieves a specific performance target by the end of 2019 and she remains an employee [Member]
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 [Member] | Common Stock [Member] | Achieves a specific performance target by the end of 2017 and she remains an employee [Member] [Member]
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 [Member] | Common Stock [Member] | Achieved performance target for 2015 and 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Value of stock to be granted if performance targets are achieved							$ 100,000
Executive Vice President and Chief Financial Officer [Member] | Common Stock [Member] | Achieved performance target for 2015, 2016 and 2017 [Member]
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
Executive Vice President and Chief Financial Officer [Member] | Common Stock [Member] | Subsequent Event [Member] | Achieved performance target for 2015 and 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of shares approved upon meeting target (in shares)				100,000
Restricted Stock [Member]
Restricted Stock
Beginning balance (in shares)	245,094
Granted (in shares)	190,276
Exercised (in shares)	(216,340)
Forfeited (in shares)	(714)
Ending balance (in shares)	218,316	245,094
Weighted-Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 24.81
Granted (in dollars per share)	26.49	$ 20.34	$ 21.27
Exercised (in dollars per share)	23.47
Forfeited (in dollars per share)	29.54
Ending balance (in dollars per share)	27.59	24.81
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)	$ 26.49	$ 20.34	$ 21.27
Total fair value of restricted shares that vested	$ 5,079,000	$ 6,507,000	$ 4,933,000
Stock Options [Member]
Stock Options
Beginning balance (in shares)	569,342
Granted (in shares)	0
Exercised (in shares)	(253,268)
Forfeited (in shares)	(2,000)
Expired (in shares)	(8,200)
Ending balance (in shares)	305,874	569,342
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 19.35
Granted (in dollars per share)	0.00
Forfeited (in dollars per share)	12.22
Exercised (in dollars per share)	27.75
Expired (in dollars per share)	24.85
Ending balance (in dollars per share)	$ 12.29	$ 19.35
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Aggregate intrinsic value of stock options outstanding	$ 6,700,000
Weighted average remaining contract life	2 years 15 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	$ 1,242,000	$ 2,350,000	$ 2,473,000
Performance Shares [Member] | Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares excluded from shares outstanding (in shares)	49,682	79,619
Weighted percentage assigned to achieving market targets	60.00%
Weighted percentage assigned to achieving performance targets	40.00%
Shares approved, maximum number of shares available in year two (in shares)	163,712
Shares approved, maximum number of shares available in year three (in shares)	137,036
Performance period	3 years