Summary of Significant Accounting Policies Reconciliation of Basic to Diluted Weighted Average Shares Outstanding (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Weighted average shares outstanding – basic (in shares)	50,038	49,415	48,816
Dilutive effect of stock options (in shares)	0	0	1,018
Weighted average shares outstanding – diluted (in shares)	50,038	49,415	49,834