Reconciliation of Weighted Average Shares Used in Calculating Basic and Diluted Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share Disclosure [Line Items]
Basic	47,991	48,551	49,522	53,325	56,405	64,208	49,034	60,316	48,682	57,966	48,431	56,281	69,689
Effect of exercise of stock options	987	1,016	1,117	1,158	1,145	1,066	1,061	1,106	1,036	1,123	804	1,137	987
Effect of contingent common stock issuance													36
Effect of assumed vesting of performance related restricted stock-based awards	381			180					127	60	212	199
Effect of assumed vesting of restricted stock	1,387	1,339	1,382	1,489	1,444	1,418	1,361	1,431	1,369	1,450	1,354	1,432	1,245
Effect of convertible notes and warrants subject to conversion	5,753	5,743	4,893	1,653			5,240		5,411	551	6,565	1,685
Effect of convertible notes warrants subject to conversion	1,958	1,946	1,137				1,541		1,681
Diluted	58,457	58,595	58,051	57,805	58,994	66,692	58,237	62,853	58,306	61,150	57,366	60,734	71,957