Share-Based Compensation - Summary of Activity for Outstanding Stock Options (Details) - Employee Stock Option - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Options
Beginning balance (in shares)	648	675	1,394
Granted (in shares)	0	184	216
Exercised (in shares)	(2)	(211)	(934)
Forfeited (in shares)	0	0	(1)
Ending balance (in shares)	646	648	675
Exercisable at end of year (in shares)	186	128	280
Weighted Average Exercise Price, Stock Options
Beginning balance (in dollars per share)	$ 40.08	$ 29.55	$ 30.85
Granted (in dollars per share)	0.00	44.07	38.73
Exercised (in dollars per share)	28.33	9.90	33.61
Forfeited (in dollars per share)	0.00	0.00	29.11
Ending balance (in dollars per share)	40.12	40.08	29.55
Exercisable (in dollars per share)	$ 38.18	$ 37.59	$ 16.38