Share-Based Compensation - Nonvested share activity and related fair value (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Nonvested Stock Shares, Weighted Average Grant Date Fair Value
Compensation expense	$ 51,565	$ 57,716	$ 51,514
Nonvested stock awards
Nonvested Stock Shares
Nonvested at the beginning of the period (in shares)	5,088,640
Granted (in shares)	1,561,155
Vested (in shares)	(2,061,297)
Forfeited (in shares)	(494,738)
Nonvested at the end of the period (in shares)	4,093,760	5,088,640
Nonvested Stock Shares, Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 27.26
Granted (in dollars per share)	20.87
Vested (in dollars per share)	32.02
Forfeited (in dollars per share)	24.23
Nonvested at the end of the period (in dollars per share)	$ 22.79	$ 27.26
Compensation expense	$ 51,600	$ 57,700	51,500
Related income tax benefit recognized	10,000	12,200	19,200
Remaining unamortized expense of nonvested stock expected to be recognized	$ 60,600
Period for expense amortized	2 years 2 months 12 days
Total fair value of shares vested	$ 41,000	$ 20,800	$ 26,700
Cash Settled RSU Plan
Nonvested Stock Shares
Nonvested at the beginning of the period (in shares)	1,213,029
Granted (in shares)	1,105,087
Vested (in shares)	(343,711)
Forfeited (in shares)	(212,345)
Nonvested at the end of the period (in shares)	1,762,060	1,213,029