Share-Based Compensation - Nonvested share activity and related fair value (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nonvested Stock Shares, Weighted Average Grant Date Fair Value
Compensation expense	$ 56,772	$ 46,613	$ 51,565
Nonvested stock awards
Nonvested Stock Shares
Nonvested at the beginning of the period (in shares)	3,641,985
Granted (in shares)	1,659,004
Vested (in shares)	(1,649,155)
Forfeited (in shares)	(111,478)
Nonvested at the end of the period (in shares)	3,540,356	3,641,985
Nonvested Stock Shares, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 19.60
Granted (in dollars per share)	13.01
Vested (in dollars per share)	20.31
Forfeited (in dollars per share)	17.64
Nonvested at the end of the period (in dollars per share)	$ 16.24	$ 19.60
Compensation expense	$ 56,800	$ 46,600	51,600
Related income tax benefit recognized	13,800	11,100	11,900
Remaining unamortized expense of nonvested stock expected to be recognized	$ 38,300
Period for expense amortized	2 years 3 months 18 days
Total fair value of shares vested	$ 26,200	$ 29,100	$ 41,000
Cash Settled RSU Plan
Nonvested Stock Shares
Nonvested at the beginning of the period (in shares)	2,375,600
Granted (in shares)	2,251,698
Vested (in shares)	(772,384)
Forfeited (in shares)	(124,828)
Nonvested at the end of the period (in shares)	3,730,086	2,375,600