Stock Benefit Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2014	Feb. 08, 2012
Stock Benefit Plans
Allocated share-based compensation expense		$ 19,530	$ 13,274	$ (46,684)
Stock Options
Stock Benefit Plans
Percent based on historical data		75.00%
Percent based on forward-looking data		25.00%
Long Term Incentive Plan
Stock Benefit Plans
Number of additional shares authorized (in shares)	4,000,000
Shares available for future grant (in shares)		4,375,000
Long Term Incentive Plan | Stock Options
Stock Benefit Plans
Options to purchase common stock outstanding (in shares)		4,797,000	6,408,000
Award vesting period		4 years
Expiration period		10 years
Compensation cost not yet recognized		$ 5,600
Period for recognition		2 years 5 months 4 days
Unvested stock options outstanding (in shares)							10,000,000.0
Threshold for accumulated accrued dividend distribution to receive cash dividends (in shares)		1,000
Threshold for accumulated accrued dividend distribution to receive stock dividends (in shares)		1,000
Granted (in shares)		9,000	2,000,000.0	1,500,000
Long Term Incentive Plan | 2017 Performance Award
Stock Benefit Plans
Allocated share-based compensation expense		$ 19,100	$ 13,000	$ 15,500
Modified EBITDA for additional performance award						$ 600,000
Unrecognized share-based compensation		$ 0
Long Term Incentive Plan | 2020 Performance Award
Stock Benefit Plans
Modified EBITDA for additional performance award					$ 750,000
Potential grants based on performance criteria (in shares)		1,025,000
Long Term Incentive Plan | Restricted Stock And Restricted Stock Units
Stock Benefit Plans
Nonvested, number (in shares)		1,581,000
Long Term Incentive Plan | Deferred Stock Units
Stock Benefit Plans
Compensation cost not yet recognized		$ 0
Number of Shares to be Issued for each award (in shares)		1
Period after which shares are to be delivered		30 days
Granted (in shares)		7,000	4,000	3,000
Weighted average grant date fair value of stock awards granted (in dollars per share)		$ 31.43	$ 50.12	$ 57.04
Total grant date fair value of stock awards granted		$ 200	$ 200	$ 200
Long Term Incentive Plan | Dividend Equivalent Rights
Stock Benefit Plans
Allocated share-based compensation expense		300	5,000	5,900
Employee Stock Purchase Plan
Stock Benefit Plans
Allocated share-based compensation expense		$ 452	$ 237	$ 285
Percentage of the market value of common stock at beginning or end of the offering period for shares eligible to be purchased		90.00%
Number of shares of common stock that may be issued under the Plan (in shares)		2,000,000
Shares in ESOP (in shares)		1,579,000