Employee Benefit Plans - Schedule of Non-Vested RSUs (Detail) - RSUs [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Nonvested Restricted Stock Units Activity [Line Items]
Non-vested, beginning balance	2,083	1,814	2,003
Shares, Restricted stock granted	1,467	1,359	1,104
Shares, Restricted stock vested	(761)	(787)	(925)
Shares, Restricted stock forfeited	(510)	(303)	(368)
Non-vested, ending balance	2,279	2,083	1,814
Weighted average grant date fair value, Non-vested, beginning balance	$ 43.34	$ 40.53	$ 35.91
Weighted average grant date fair value, Restricted stock granted	35.89	43.35	41.61
Weighted average grant date fair value, Restricted stock vested	42.74	38.34	32.39
Weighted average grant date fair value, Restricted stock forfeited	41.51	39.54	39.08
Weighted average grant date fair value, Non-vested, ending balance	$ 39.16	$ 43.34	$ 40.53