Stock-Based Compensation - Performance-Based Stock Grants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock options | Class A Non-Voting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based award vesting period	3 years
Weighted-Average Grant-Date Fair Value
Share-based compensation expense	$ 1,397	$ 1,253	$ 1,233
Unearned compensation cost	$ 889
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based award vesting period	3 years
Performance shares | Class A Non-Voting
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based award vesting period	3 years
Shares
Nonvested at the beginning of the period (in shares)	988,837	884,342	806,881
Granted (in shares)	626,776	751,128	930,295
Vested (in shares)	(214,824)	(445,311)	(668,649)
Forfeited or unearned (in shares)	(427,010)	(201,322)	(184,185)
Nonvested at the end of the period (in shares)	973,779	988,837	884,342
Weighted-Average Grant-Date Fair Value
Nonvested at the beginning of the period, weighted-average grant-date fair value (in usd per share)	$ 8.07	$ 7.05	$ 6.17
Granted, weighted-average grant-date fair value (in usd per share)	8.87	7.43	7.54
Vested, weighted-average grant-date fair value (in usd per share)	8.49	5.98	5.38
Forfeited or unearned, weighted-average grant-date fair value (in usd per share)	8.34	7.54	5.85
Nonvested at the end of the period, weighted-average grant-date fair value (in usd per share)	$ 8.38	$ 8.07	$ 7.05
Fair value of performance shares vested	$ 1,823	$ 2,662	$ 3,597
Share-based compensation expense	1,082	$ 3,307	$ 3,796
Unearned compensation cost	$ 2,212