Share-Based Compensation Plans - Summary of Activity Related to Restricted Stock Granted under Incentive Plan (Detail) - Restricted Stock Grants [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shares, Granted	264	315	308
Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shares, Outstanding, Beginning Balance	1,056	1,033	983
Total Shares, Granted	275	324	317
Total Shares, Vested	(329)	(274)	(225)
Total Shares, Forfeited, canceled or expired	(9)	(27)	(42)
Total Shares, Outstanding, Ending Balance	993	1,056	1,033
Weighted Average Grant Date Fair Value, Beginning Balance	$ 34.30	$ 28.75	$ 21.34
Weighted Average Grant Date Fair Value, Granted	44.46	45.66	46.02
Weighted Average Grant Date Fair Value, Vested	30.56	27.18	21.27
Weighted Average Grant Date Fair Value, Forfeited, cancelled or expired	37.94	30.27	27.36
Weighted Average Grant Date Fair Value, Ending Balance	$ 38.32	$ 34.30	$ 28.75