Share-Based Compensation - Summary of Nonvested Restricted Stock Unit Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock Units Activity [Abstract]
Number of Shares, Nonvested beginning balance	1,014,000	1,136,000	1,169,000
Number of Shares, Granted	283,000	280,000	429,000
Number of Shares, Vested	(404,000)	(321,000)	(413,000)
Number of Shares, Forfeited	(99,000)	(81,000)	(49,000)
Number of Shares, Nonvested ending balance	794,000	1,014,000	1,136,000
Weighted Average Grant Date Fair Value, Nonvested beginning balance	$ 14.88	$ 12.30	$ 11.40
Weighted Average Grant Date Fair Value, Granted	27.99	22.70	13.20
Weighted Average Grant Date Fair Value, Vested	14.26	11.90	10.80
Weighted Average Grant Date Fair Value, Forfeited	17.79	13.78	11.14
Weighted Average Grant Date Fair Value, Nonvested ending balance	$ 19.51	$ 14.88	$ 12.30