Long-term Equity-based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) installment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (in shares) | shares	7,000,000
Shares available for grant (in shares) | shares	6,734,289
Share-based compensation expense	$ 24,900	$ 25,300	$ 18,600
Total compensation cost not yet recognized	$ 24,600
Annual awards of deferred stock units to be issued to each non-employee director, aggregate fair value		$ 110
Weighted-average grant-date fair values (in dollars per share) | $ / shares	$ 19.24	$ 20.99	$ 15.14
Total intrinsic value	$ 7,100	$ 7,700	$ 3,900
Cash received from exercises of awards	5,000	2,400	900
Total tax benefit realized for tax deductions from exercise of awards	1,500	1,600	800
Total fair value of DSUs that vested during the years	$ 0	0	1,000
Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in share authorization if maximum performance level is met or exceeded (in shares) | shares	1,534,158
Award vesting period	3 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting installments | installment	3
Award vesting period	3 years
Expiration period	10 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual awards of restricted stock units to be issued to each non-employee director, aggregate fair value	$ 130
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of vested awards	20,400	24,800	8,700
Tax benefits for tax deductions realized from awards	$ 4,300	$ 5,200	$ 1,800
Performance Period 1 | Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in share authorization if maximum performance level is met or exceeded (in shares) | shares	746,670
Number of additional shares to be granted if maximum performance level is met or exceeded (in shares) | shares	248,890
Performance Period 2 | Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in share authorization if maximum performance level is met or exceeded (in shares) | shares	404,574
Number of additional shares to be granted if maximum performance level is met or exceeded (in shares) | shares	134,858
Performance Period 3 | Performance Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reduction in share authorization if maximum performance level is met or exceeded (in shares) | shares	382,914
Number of additional shares to be granted if maximum performance level is met or exceeded (in shares) | shares	127,638